Compact high power alternator

ABSTRACT

An apparatus for converting between mechanical and electrical energy, particularly suited for use as a compact high power alternator for automotive use and “remove and replace” retrofitting of existing vehicles. The apparatus comprises a rotor with permanent magnets, a stator with a winding, and a cooling system. Mechanisms to prevent the rotor magnets from clashing with the stator by minimizing rotor displacement, and absorbing unacceptable rotor displacement are disclosed. The cooling system directs coolant flow into thermal contact with at least one of the winding and magnets, and includes at least one passageway through the stator core. Various open and closed cooling systems are described. Cooling is facilitated by, for example, loosely wrapping the winding end turns, use of an asynchronous airflow source, and/or directing coolant through conduits extending through the stator into thermal contact with the windings.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 60/486,831, filed Jul. 10, 2003, by inventors Charles Y. Lafontaineand Harold C. Scott.

BACKGROUND OF THE INVENTION

The present invention relates to machines for converting betweenmechanical and electrical energy, and in particular to a compact highpower alternator using permanent magnets suitable for automotive use.

An alternator typically comprises a rotor mounted on a rotating shaftand disposed concentrically relative to a stationary stator.Alternatively, a stationary rotor may be positioned concentricallywithin a rotating stator. An external energy source, such as a motor orturbine, commonly drives the rotating element, directly or through anintermediate system such as a pulley belt. Both the stator and the rotorhave a series of poles. Either the rotor or the stator generates amagnetic field, which interacts with windings on the poles of the otherstructure. As the magnetic field intercepts the windings, an electricalcurrent is generated, which is provided to a suitable load. The inducedcurrent is typically applied to a bridge rectifier, sometimes regulated,and provided as an output. In some instances, the regulated outputsignal is applied to an inverter to provide an AC output.

Conversely, the device can act as a motor if an appropriate electricalsignal is applied to the windings.

Conventionally, alternators employed in automotive applicationstypically comprise: a housing, mounted on the exterior of an engine; astator having 3-phase windings housed in the housing, a belt-drivenclaw-pole type (e.g., Lundell) rotor rotatably supported in the housingwithin the stator. However, the power output of such conventionalclaw-pole type alternators is directly proportional to the size of thealternator; to increase power output the size of the conventionalalternator must be significantly increased. Accordingly, spaceconstraints in vehicles tend to make such alternators difficult to usein high output, e.g., 5 kW, applications, such as for powering airconditioning, refrigeration, or communications apparatus. In addition,claw-type generators are also disadvantageous in that voltage regulationis by modulating the rotating field. Such modulation affects all of thewindings. Accordingly, voltage regulation and control of individualwindings is impractical.

In addition, the claw-pole type rotors, carrying windings, arerelatively heavy (often comprising as much as half of the total weightof the alternator) and create substantial inertia. Such inertia, ineffect, presents a load on the engine each time the engine isaccelerated. This tends to decrease the efficiency of the engine,causing additional fuel consumption. Reductions in the mass and diameterof rotating components of an alternator will tend to reduce the overallinertia an engine has to overcome, thereby improving fuel economy. Apermanent magnet alternator is ideally suited for reducing overallinertia. The mass and diameter of rotating components are reduced ascompared to that of conventional Lundell alternators, while supplying anequivalent amount of power.

A reduction of inertia in a motor vehicle alternator also translates toa reduction in horsepower required by the engine to accelerate thealternator. The savings in horsepower could then conceivably be appliedto a vehicle drive train resulting in more power to propel the vehicle.This would be of great interest for example, to race car engineers whomust deal with regulations limiting horsepower generated by raceengines. Even a slight improvement in available horse power to the drivewheels can yield a tremendous competitive advantage.

In addition, such inertia can be problematical in applications such aselectrical or hybrid vehicles. Hybrid vehicles utilize a gasoline engineto propel the vehicle at speeds above a predetermined threshold, e.g. 30kph (typically corresponding to a range of RPM where the gasoline engineis most efficient). Similarly, in a so-called “mild hybrid,” astarter-generator is employed to provide an initial burst of propulsionwhen the driver depresses the accelerator pedal, facilitating shuttingoff the vehicle engine when the vehicle is stopped in traffic to savefuel and cut down on emissions. Such mild hybrid systems typicallycontemplate use of a high-voltage (e.g. 42 volts) electrical system. Thealternator in such systems must be capable of recharging the battery tosufficient levels to drive the starter-generator to provide the initialburst of propulsion between successive stops, particularly in stop andgo traffic. Thus, a relatively high power, low inertia alternator isneeded.

In general, there is in need for additional electrical power forpowering control and drive systems, air conditioning and appliances invehicles. This is particularly true of vehicles for recreational,industrial transport applications such as refrigeration, constructionapplications, and military applications.

For example, there is a trend in the automotive industry to employintelligent electrical, rather than mechanical or hydraulic control anddrive systems to decrease the power load on the vehicle engine andincreased fuel economy. Such systems may be employed, for example, inconnection with steering servos (which typically are active only asteering correction is required), shock absorbers (using feedback toadjust the stiffness of the shock absorbers to road and speedconditions), air conditioning (operating the compressor at the minimumspeed required to maintain constant temperature). The use of suchelectrical control and drive systems tends to increase the demand on theelectrical power system of the vehicle.

Similarly, it is desirable that mobile refrigeration systems beelectrically driven. For example, efficiency can be increased by drivingthe refrigeration system at variable speeds (independently of thevehicle engine rpm). In addition, with electrically driven systems thehoses connecting the various components, e.g. the compressor (on theengine), condenser (disposed to be exposed to air), and evaporation unit(located in the cold compartment), can be replaced by an electricallydriven hermetically sealed system analogous to a home refrigerator orair-conditioner. Accordingly, it is desirable that a vehicle electricalpower system in such application be capable of providing the requisitepower levels for an electrically driven unit.

There is also a particular need for a “remove and replace” high poweralternator to retrofit existing vehicles. Typically only a limitedamount of space is provided within the engine compartment of the vehicleto accommodate the alternator. Unless a replacement alternator fitswithin that available space, installation is, if possible, significantlycomplicated, typically requiring removal of major components such asradiators, bumpers, etc. and installation of extra brackets, belts andhardware. Accordingly, it is desirable that a replacement alternator fitwithin the original space provided, and interface with the originalhardware.

In general, permanent magnet alternators are well-known. Suchalternators use permanent magnets to generate the requisite magneticfield. Permanent magnet generators tend to be much lighter and smallerthan traditional wound field generators. Examples of permanent magnetalternators are described in U.S. Pat. No. 5,625,276 issued to Scott etal on Apr. 29, 1997; U.S. Pat. No. 5,705,917 issued to Scott et al onJan. 6, 1998; U.S. Pat. No. 5,886,504 issued to Scott et al on Mar. 23,1999; U.S. Pat. No. 5,929,611 issued to Scott et al on Jul. 27 1999;U.S. Pat. No. 6,034,511 issued to Scott et al on Mar. 7, 2000; and U.S.Pat. No. 6,441,522 issued to Scott on Aug. 27, 2002.

Particularly light and compact permanent magnet alternators can beimplemented by employing an “external” permanent magnet rotor and an“internal” stator. The rotor comprises a hollow cylindrical casing withhigh-energy permanent magnets disposed on the interior surface of thecylinder. The stator is disposed concentrically within the rotor casing.Rotation of the rotor about the stator causes magnetic flux from therotor magnets to interact with and induce current in the statorwindings. An example of such an alternator is described in, for example,the aforementioned U.S. Pat. No. 5,705,917 issued to Scott et al on Jan.6, 1998 and U.S. Pat. No. 5,929,611 issued to Scott et al on Jul. 271999.

The stator in such permanent magnet alternators is suitably comprised ofindividual thin steel laminations of an appropriate shape and chemicalcomposition which are then welded or epoxied together in a cylindricalbody with teeth and slots to accept windings. The respective laminationsof the stack are positioned in both axial and rotational alignment sothat the resultant state or teeth and slots are aligned (disposed)axially. The power output wave produced by axially aligned teeth andslots is by its nature a square wave.

However, it would be advantageous in applications employing controlsystems dependant on synchronization with the output, to have a poweroutput wave with sloping sides to enhance control timing.

The power supplied by a permanent magnet generator varies significantlyaccording to the speed of the rotor. In many applications, changes inthe rotor speed are common due to, for example, engine speed variationsin an automobile, or changes in load characteristics. Accordingly, anelectronic control system is typically employed. An example of apermanent magnet alternator and control systems therefor is described inthe aforementioned U.S. Pat. No. 5,625,276 issued to Scott et al on Apr.29, 1997. Examples of other control systems are described in U.S. Pat.No. 6,018,200 issued to Anderson, et al. on Jan. 25, 2000.

However, in such permanent magnet alternators, the efficiency isinversely proportional to the “air gap” separating the magnets from thestator. Such air gaps are often in the range of 20 to 40 thousands of aninch. With such close spacing/tolerances, the permanent magnetalternators are particularly susceptible to destructive interference(clashing) between magnets and stator as a result of displacement of therotor caused by external forces acting on the alternator. In vehicularapplications relatively severe external forces are commonplace, due to,for example, engine vibration (particularly diesel engines at startup),cornering, traversing bumpy roads or terrain, and other types of impact.Accordingly, an alternator in which rotor displacement is minimized, andwhich includes a mechanism to absorb unacceptable rotor displacement andprevent the rotor magnets from clashing with the stator is needed.

The use of a taper at the end of a motor shaft to center an attachment,e.g. attaching lawn mower blades to a motor shaft, is known.Conventionally, such a taper is provided only at the end of a shaft. Anaxial tapped hole is provided in the shaft end surface. The attachmentincludes a hub with a corresponding tapered aperture. However, thetapered aperture typically extends only partway (as opposed to through)the attachment hub; it is, in effect, a countersink to a smallerdiameter through bore. The attachment is secured to the shaft by a boltpassing through the attachment hub bore and threaded into the hole inthe shaft end surface. The tapered connection tends to center theattachment on the shaft, however, the attachment on the end of theshaft, is, in effect, cantilevered and susceptible to vibrationaloscillations.

In addition, the heat generated by compact high power alternators canalso be problematical. This is particularly true in applications wheresignificant levels of power are generated at relatively low engine rpm;in general; the amount of air moved by a fan is proportional to thesquare of the fan rpm. As alternators become more compact and moreefficient, significant levels of heat are generated. Permanent magnetsare particularly susceptible to damage due to overheating; under highload, high temperature conditions, such magnets can become demagnetized.Similarly, the electronic components employed in the controller aresusceptible to heat damage. Accordingly, a strategy must be developed todissipate heat buildup.

Use of airflow to cool heat generating elements (e.g., rectifiers) in agen-set are known. An example of such cooling is described in theaforementioned U.S. Pat. No. 5,929,611 issued to Scott et al on Jul. 271999. Conventionally, airflow is provided by a fan driven by the sameshaft on which the rotor is mounted. However, in various automotiveapplications, significant heat is generated at low rpm.

In general, an appreciable reduction in diameters would be employed toachieve a useful reduction in inertia. This tends to create an acuteneed for cooling in reduced inertia alternators. The reduction in bothmass and overall diameters of these alternators tends to make the use ofconventional cooling methods impractical.

Cooling techniques that permit a permanent alternator to be fully sealedare desirable in situations where exposure to the elements would bedetrimental to the operation of the alternator. This is of particularinterest to the military or any application subjected to harsh, dustyenvironments which would be detrimental to the magnets due to theiraffinity to ferrous particles found in most sand.

There also is a need for an alternator that can accommodate not only thepower levels, but also the space and ruggedness constraints imposed byuse in vehicles. For example, operation of a vehicle tends to generateforces perpendicular to the axis of the rotor that are sometimessufficient to cause the rotor and stator to clash. The rotor and statorare separated only by a small air gap, and the external forces tend tocause transverse movement of the rotor in excess of the air gap thenthere will be striking interference.

SUMMARY OF THE INVENTION

The present invention provides particularly advantageous machine forconverting between mechanical and electrical energy.

Various aspects of the invention provide a compact power conversionapparatus using permanent magnets that can accommodate not only thepower levels, but also the space and ruggedness constraints imposed byuse in vehicles. Another aspect of the invention provides a “remove andreplace” high power alternator to retrofit existing vehicles.

Other aspects of the invention provide a compact high power conversionapparatus using permanent magnets in which rotor displacement isminimized, and which includes a mechanism to absorb unacceptable rotordisplacement and prevent the rotor magnets from clashing with thestator.

In accordance with another aspect of the invention a power conversionapparatus comprises a rotor, a stator, and a cooling system.

The rotor comprises a cylindrical casing, and a predetermined number ofpermanent magnets disposed in the interior of the casing, and is adaptedfor rotation about the axis of the casing.

The stator comprises a core and at least one conductive winding. Thecore includes a generally cylindrical outer peripheral surface with apredetermined number of slots formed therein. The winding is woundaround the core through the slots.

The stator is concentrically disposed within the interior of the rotorcasing, with the stator core peripheral surface disposed proximate tothe rotor magnets, separated from the magnets by a predetermined gapdistance, such that relative motion of the rotor and stator causesmagnetic flux from the magnets to interact with and induce current inthe stator winding.

The cooling system directs coolant flow into thermal contact with atleast one of the winding and magnets, and includes at least onepassageway through the stator core.

In accordance with other aspects of the present invention, cooling isfacilitated by one or more of: loosely wrapping winding end turns to, ineffect, increase the surface area of the windings; establishing adirected airflow over at least a portion the stator windings,(preferably through loosely wrapped end turns of the windings);directing a portion of the airflow over elements in thermal contact withthe magnets; providing airflow from a source that is asynchronous withrespect to the shaft on which the rotor is mounted, e.g. an electricfan; and directing a flow of coolant fluid into thermal contact with thewinding end turns.

BRIEF DESCRIPTION OF THE DRAWING

The present invention will hereinafter be described in conjunction withthe figures of the appended drawing, wherein like designations denotelike elements, and:

FIG. 1 is a front view of a first embodiment of an alternator inaccordance with the present invention (with windings removed forclarity).

FIG. 2 is a side view of the alternator of FIG. 1.

FIG. 3 is a schematic sectional view (taken along line BB in FIG. 2) ofthe alternator of FIGS. 1 and 2 (with windings shown schematically).

FIG. 4A is a schematic sectional view (taken along line CC in FIG. 2) ofthe alternator of FIGS. 1, 2 and 3 (with windings shown onlyschematically for clarity).

FIG. 4B is a schematic sectional view (taken along line CC in FIG. 2) ofthe alternator of FIGS. 1, 2 and 3 (with windings shown onlyschematically for clarity), modified such that the tie rods are exteriorof the case.

FIG. 4C is a detail blowup of a portion of FIG. 4A.

FIG. 4D is an isometric view of an axially and rotationally alignedstator core.

FIG. 4E is an isometric view of a skewed stator core.

FIG. 4F is a sectional view detailing the mounting of the skewed statorcore of FIG. 4E.

FIG. 4G is an isometric view of a rotor utilizing magnets with anaxially aligned edge.

FIG. 4H is an isometric view of a rotor utilizing magnets with a skewededge.

(FIGS. 4A-4F are collectively referred to as FIG. 4.)

FIGS. 5A, 5B, and 5C (collectively referred to as FIG. 5) are schematicillustrations of the movement of the rotor in response to exteriorforces.

FIGS. 6A, 6B, 6C, 6D, 6E, 6F, and 6G (collectively referred to as FIG.6) are schematic sectional diagrams of respective embodiments ofmechanisms for preventing destructive interference between the rotor andstator of an alternator in accordance with the present invention.

FIG. 7A is a schematic sectional diagram of an alternator employing arotor with a conical endcap to reduce displacement of the rotor inresponse to external forces.

FIG. 7B is a diagram illustrating the wobble motion of the rotor.

FIG. 7C is a schematic sectional diagram of an alternator employing arotor with a greatly increased cross-sectional area to the endcap toreduce displacement of the rotor in response to external forces.

FIG. 7D is a schematic sectional diagram of an alternator using a rotorwith a welded rotor case.

FIG. 7E is a schematic sectional diagram of an alternator employing arotor and shaft cast as a single unit.

FIG. 8 is a schematic sectional diagram (partial) of an alternatoremploying the rotor of FIG. 7A and a combination of the mechanisms forpreventing destructive interference of FIG. 6. Gap spaces in the variousfigures of the drawing are exaggerated for clarity.

FIG. 9A is a schematic sectional diagram of an alternator employing aircooling in accordance with one aspect of the present invention.

FIG. 9B is a schematic sectional diagram of an alternator employing aircooling for the magnets and fluid cooling for the coil end turns inaccordance with another aspect of the present invention.

FIG. 9C is a schematic sectional diagram of an alternator employingfluid cooling exclusively in a sealed alternator in accordance with oneaspect of the present invention.

FIG. 9D is a detail sectional diagram of the arrangement of heatconducting encapsulant, cooling tubes and heat transfer fins in a fluidcooled alternator.

FIG. 9E is a detail of suitable routing of the cooling tubes in a fluidcooled alternator.

FIG. 10A is a simplified schematic top view of an axially aligned statorand end turns of the stator windings.

FIG. 10B is a simplified schematic top view of a skewed stator and endturns of the stator windings.

FIG. 11 is a simplified schematic perspective view of a portion of thestator and end turns of the stator windings with the end turns of thestator windings bent into the airflow.

FIG. 12 is a schematic sectional view of a first embodiment of a sealedalternator unit employing heat exchanger and internal and external fans.

FIGS. 13A and 13B (collectively referred to as FIG. 13) are schematicdiagrams of respective embodiments of a heat exchanger.

FIG. 14 is a schematic sectional view of a first embodiment of a sealedalternator unit with the external airflow supplied through an airplenum.

FIG. 15 is a schematic sectional view of a first embodiment of a locallysealed alternator unit with the external airflow supplied through adoubled walled snorkel.

FIGS. 16A and 16B (collectively referred to as FIG. 16) are schematicsectional views of the alternator of FIG. 15 utilizing repectiveembodiments of an optimized fan.

FIG. 17 is a schematic sectional view of the alternator of FIG. 15utilizing an alternative embodiment of an optimized fan.

FIGS. 18A, 18B and 18C (collectively referred to as FIG. 18) areschematic diagrams of respective embodiments of airflow filteringstrategies suitable for use with alternator of FIG. 15.

FIG. 19 is a rear view of a fan housing suitable for use with alternatorof FIG. 15 employing an air conduit transverse to the axis of thealternator.

FIGS. 20A, 20B and 20C are schematic representations of filter systemssuitable for use with the optimized fans of FIGS. 16 and 17,respectively.

FIG. 21A is a schematic sectional side view electrical componentsmounted in air cooled alternator endplate.

FIG. 21B is a schematic sectional rear view (from direction A-A in FIG.21A) of the mount of FIG. 21A.

FIG. 22A is a schematic sectional side view showing electricalcomponents mounted in the fan housing of an air cooled alternator.

FIG. 22B is an isometric perspective view of the electrical componentmount of FIG. 22A.

FIG. 23A is a sectional view showing electrical components mounted in anend turn fluid cooled alternator sharing alternator fluid cooling.

FIG. 23B is a sectional view showing electrical components mounted in anall fluid cooled alternator sharing alternator fluid cooling.

DETAILED DESCRIPTION OF A PREFERRED EXEMPLARY EMBODIMENT

Referring now to FIGS. 1, 2, 3, and 4 an apparatus for convertingbetween mechanical and electrical energy, e.g., an alternator 100 inaccordance with various aspects of the present invention comprises: ashaft 110, preferably including a tapered projecting portion 310 and athreaded portion 312; a rotor 112; a stator 114; a front endplate 116; afront bearing 118; a jam nut 120; a rear endplate 122; a rear shaftretaining ring 123; a rear bearing 124; a rear jam nut 125; a rearendplate retaining ring 127; an electric fan 126; an outer casing 128and respective tie rods 130. Rotor 112 is mounted on shaft 110 forrotation with the shaft. Stator 114 is closely received within rotor112, separated from rotor 112 by a small air gap 412. Front endplate116, front bearing 118, rear bearing 124, rear endplate 122, outercasing 128 and tie rods 130 cooperate as a support assembly to maintainalignment of shaft 110, rotor 112, and stator 114. Shaft 110 ismaintained by bearings 118 and 124, which are mounted on front endplate116 and rear endplate 122, respectively, and rotatably maintain andalign shaft 110 concentric and perpendicular with the endplates. Rotor112 is mounted for rotation on shaft 110, positively positioned bycooperation with tapered shaft portion 310. Rear endplate 122 mounts andlocates stator 114 so that it is disposed within rotor 112 properlyaligned with shaft 110 and rotor 112. Outer casing 128 has end facesperpendicular to its axis (is preferably cylindrical) and is disposedbetween front endplate 116 and rear endplate 122. Tie rods 130; compressendplates 116 and 122 against outer casing 128, keeping the componentssquared and in alignment.

In a typical automotive alternator application, a pulley 132 is mountedon the end of shaft 110. Power from an engine (not shown) is transmittedthrough an appropriate belt drive (not shown) to pulley 132, and henceshaft 110. Shaft 110 in turn causes rotor 112 to rotate about stator114. Rotor 112 generates a magnetic field, which interacts with windingson stator 114. As the magnetic field intercepts the windings, anelectrical current is generated, which is provided to a suitable load.The induced current is typically applied to a bridge rectifier,sometimes regulated, and provided as an output. In some instances, theregulated output signal is applied to an inverter to provide an ACoutput.

Shaft 110 is, in general, cylindrical, of a predetermined diameter (e.g.¾ in) with larger diameter portions for accommodating pulley 132, (e.g.,⅞ in), and front bearing 118 (e.g. 1¼ in), rotor 112 (tapered portion310) and jam nut 120 (threaded portion 312, e.g. 1 in). Taperedprojecting portion 310 is disposed at a predetermined position on shaft110, and has a predetermined taper, i.e., its diameter increases from aminimum diameter (substantially equal to that of threaded portion 312)by a predetermined amount per unit of length, suitably in the range of 1in. diameter per 7 inches of length to 1 in. diameter per 16 inches oflength, and preferably 1 in. per foot. Tapered portion 310 is preferablyheld to relatively close tolerance, e.g. plus or minus 0.004°. The taperis chosen to ensure sufficient surface area contact between shaft 110and rotor 112, while still providing sufficient change in diameter toprevent unwanted axial movement of the rotor once secured.

Rotor 112 preferably comprises an endcap 314, a cylindrical casing 316and a predetermined number (e.g. 12 pairs) of alternatively poledpermanent magnets 318 disposed in the interior side wall of casing 316.FIGS. 7D and 7E will detail alternative configurations of endcap 314 andcylindrical casing 316

Rotor endcap 314 is suitably substantially open, including a peripheralportion 321, respective cross-arms 322 and a central hub 324 to providefor connection to shaft 110. Respective air passageways 323 are providedthrough endcap 314, bounded by peripheral portion 321, adjacent crossarms 322, and central hub 324. If desired, cross arms 322 can beconfigured as fan blades to facilitate cooling internal chamber 320. Aswill be more fully explained, rotor hub 324 includes a through-bore 326having a predetermined taper (e.g. 1 in. per foot) corresponding to thatof shaft portion 310. In assembly, shaft 110 is journaled through bore326, such that shaft tapered portion 310 is received in bore 326 justforward of threaded shaft portion 312. Threaded shaft portion 312cooperates with jam nut 120 to positively locate rotor 112 on shaft 110.In general, the thickness of crossarms 322 is suitably chosen to be asthin as possible (to minimize weight and material cost) while stillcapable of withstanding expected loads, suitably in the range of ⅜ in.to ⅝ inch at its thinnest point. Since rotor casing 316 is, in effect,cantilevered from endcap 314, the necessary thickness is proportional tothe length of casing 316. Rotor hub 324, in the vicinity of bore 326, issuitably thick enough to provide adequate surface contact with taperedshaft portion 310, suitably on the order of 1½ inch.

Cylindrical rotor casing 316 is formed of “soft magnetic” (relativelytransparent to magnetic flux) material (e.g. lead free steel) of apredetermined outer diameter and thickness. In general, to maximizepower output, it is desirable that the diameter D_(AG) (FIG. 4) of thecircle defined by the inner surface of magnets 318 (sometimes referredto herein as the air gap diameter) be as large as possible given theapplicable overall size constraints for alternator 100. For example, inmany automotive applications, alternator 100 must be no more than 5 in.long and 5 in. in diameter in order to fit within the available space.The thickness of casing 316 is suitably chosen to be as thin as possible(to minimize weight and material cost) while still capable ofwithstanding expected loads and without the flux density from magnets318 saturating the casing. The thickness of casing 316 is suitably inthe range of ⅛ to ½ inch, typically in the range of {fraction (3/16)} to¼ inch, and, in the embodiments of FIGS. 1-4, {fraction (3/16)} inch.

Magnets 318 preferably comprise high energy product magnets having aflux density of at least on the order of five kilogauss, preferablyranging from eight to 11 kilogauss, suitably formed of a rare earthalloy such as neodymium iron boron, or samarium cobalt. Such rare earthmaterials tend to be extremely expensive, and, accordingly, it isdesirable to minimize the amount of material used. However, at the sametime, it is desirable to generate relatively high flux densities. In thepreferred embodiment, magnets 802 are relatively thin, e.g. on the orderof 0.1 to 0.15 an inch thick, but present a relatively large area, 0.75inch wide by from approximately one inch to 2.5 in. long , to minimizethe amount of high energy product magnet used.

Magnets 318 may be secured to casing 316 in any suitable manner. Forexample, magnets 318 may be glued to casing 316. The disposition ofmagnets 318 on the interior of casing 316 is advantageous in that, interalia, magnetic force tends to secure magnets 318 to casing 316; even inthe event that the adhesive fails, the magnets will tend to stay inplace. If desired, in some applications where less power density isacceptable, soft magnetic consequence poles 318A may be employed inplace of one set of permanent magnet poles.

Stator 114 suitably comprises a core 328 and conductive windings 330(FIG. 3, shown only schematically). As best seen in FIG. 4, core 328 isgenerally cylindrical, with an axially crenellated outer peripheralsurface, i.e., includes a predetermined number of teeth 402 and slots404. Core 328 is preferably substantially open (except in an all fluidcooled alternator as will be discussed), with a central aperture 406defined by the cylindrical interior surface 407 of core 328.

One embodiment of core 328 suitably includes crossarms 408 extendingradially inward from surface 407. Crossarms 408 suitably include axialthrough-bores 410 to facilitate mounting core 328 to rear endplate 122.As best seen in FIG. 3, stator core 328 may be secured to rear endplate122 by respective bolts 352 journaled through bores 410 and secured intapped holes 350.

Core 328 suitably comprises a laminated stack of thin sheets of softmagnetic material, e.g. non-oriented, low loss (lead free) steel, thatare cut or punched to the desired shape, aligned and joined (e.g.,welded or epoxied together in a precision jig to maintain the separatelaminations in predetermined alignment). In general, the respectivelaminations are axially and rotationally aligned so that the resultantstate or teeth and slots are straight, aligned (disposed) parallel tothe core axis, as illustrated in FIG. 4D.

However, it is advantageous, in applications employing control systemsdependant on synchronization with the output, to have a power outputwave with a particular waveform, e.g., sloping sides, to enhance controltiming. This can be accomplished by establishing progressive (gradual)interaction between the rotor magnets and core teeth. Such progressiveinteraction can be provided by, for example, by utilizing teeth andslots with an edge skewed with respect to magnets 318, e.g., manifestinga generally helical shape. In a laminar core such teeth and slots can beformed using a slight and progressive radial skewing of each successivelamination so that the net effect after welding or epoxying is alamination stack with a predetermined offset in the radial position of agiven tooth from the front face of the lamination stack to the rearface. In the preferred embodiment, the offset is the equivalent of onetooth (e.g., the “^(th)” tooth on the front face is aligned with tooth“n+1” on the rear face). The predetermined amount of offset is suitablyany offset up to the equivalent of approximately 1 tooth, and preferablyranges from the equivalent of approximately 0.01 to approximately 1tooth. An example of such a “skewed core” embodiment of core 328,designated 329, is shown in FIG. 4E. (Except when specificallyotherwise, references hereinafter to core 328 are intended to refer toboth the axially aligned embodiment of core 328 and the skewedembodiment 329.)

As shown in FIG. 4F, if crossarms 408 are omitted, e.g. as in skewedcore 329, core 328 may be secured to rear endplate 122 using a suitablemounting ring 412, including a locating shoulder and throughbores 416(corresponding to crossarm bores 410) cooperating with bolts 352 (inlieu of crossarms 408). In most cases, sufficient torque applied tomounting bolts 352 will be adequate to prevent rotation of core 328relative to mounting ring 412 and rear endplate 122. However, if desireda suitable fastening method, such as, for example, epoxy, a pin, or key,can be incorporated to help prevent rotation of the lamination stackwhen in use.

Progressive (gradual) interaction between the rotor magnets and coreteeth can also be provided by skewing the edge of magnets 318 by apredetermined amount relative to the stator teeth. For example, a rotorutilizing magnets with a skewed edge is shown in FIG. 4H. For contrast,a rotor utilizing magnets with an axially aligned edge is shown in FIG.4G. As in the case of the skewed core, the predetermined amount ofoffset is suitably any offset up to the equivalent of approximately 1tooth, and preferably ranges from the equivalent of approximately 0.01to approximately 1 tooth.

Windings 330, formed of a suitably insulated electrical conductor,preferably varnished copper motor wire, are provided on core 328, woundthrough a respective slot 404, outwardly along the side face of core 328around a predetermined number of teeth 402, then back through anotherslot 404. The portion of windings 330 extending outside of slots 404along the side faces of core 328 are referred to herein as front-sideand rear-side end turns 332A and 332B, respectively (collectivelyreferred to as end turns 332). Conventionally, end turns 332 of windings330 are drawn tightly against the side face of core 328 to minimize theamount of wire (and hence impedance) in the windings. However as will befurther discussed, in accordance with one aspect of the presentinvention, cooling may be facilitated by loosely winding end turns 332,such that end turns 332 extend outwardly from core 328 providing airspaces between the various wires and core 328.

If desired, windings 330 may be separated into a predetermined number ofphases and/or into independent groups as described in the aforementionedScott et al. U.S. Pat. No. 5,625,276.

In assembly, stator 114 is disposed coaxially with rotor 112, and isclosely received within interior cavity 320 of rotor 112. As will beexplained, rear endplate 122 mounts and locates stator 114 so that it isproperly aligned within internal chamber 320 of rotor 112. Theperipheral surface of stator core 328 is separated from the interiorsurface of magnets 318 by a small predetermined air gap 412 (best seenin FIG. 4B). Air gap 412 is suitably in the range of 20 to 40 thousandsof an inch, and in the embodiments of FIGS. 1-4 on the order of 30thousands of an inch, e.g., 31 thousands of an inch. Accordingly, theinner diameter of casing 316, magnets 318, and outer diameter of statorcore 328 are preferably held to close tolerances to maintain alignment.It is important that rotor 112 and stator 114 be carefully aligned, anddisplacement of the elements from their normal positions due to externalforces on the alternator held below a threshold value.

As noted above, alignment of shaft 110, rotor 112, and stator 114achieved by a bearing structure comprising front endplate 116, frontbearing 118, rear bearing 124, rear endplate 122, outer casing 128 andtie rods 130. Bearings 118 and 124, in effect, provide respective pointsof rotatable connection between shaft 110 and the bearing structure.Bearings 118 and 124, and hence shaft 110, are disposed concentric andperpendicular with endplates 116 and 122, respectively. Rotor 112 ispreferably positively positioned with respect to shaft 110 throughcooperation of tapered rotor hub through bore 326 and tapered shaftportion 310. Stator 114 is located relative to and aligned with shaft110, and hence rotor 112, by rear endplate 122. The alignment ofendplates 116 and 122 is maintained by outer casing 128 and tie rods130.

Front endplate 116 is suitably generally cylindrical, including: acentrally disposed hub, including a coaxial aperture 334 with acounterbore 336; a peripheral portion 133 including respective (e.g.eight) tapped holes 337 disposed at predetermined radial distances fromthe center of aperture 334, distributed at equal angular distances, toreceive tie rods 130; and respective (e.g., 4) crossarms 134 connectingperipheral portion 133 to hub 333, and defining respective air passages136. Front endplate 116 is dimensioned and machined to high tolerance(e.g. plus or minus 0.0008 TYP for counterbore 336, 0.005 TYP for otherfeatures, such as tie rod hole 337 patterns, outer case shoulder,mounting hole patterns), suitably formed of metal e.g. cast aluminum,and should be sufficiently strong to withstand the rotational loadscreated by the turning of shaft 110 and rotor 112, as well as sideloading that occurs as a result of the belt pulling on pulley 132. Frontbearing 118 is closely received in counterbore 336 and suitably secured,e.g. by a suitable retaining ring 338. Front endplate 116 thus locatesfront bearing 118 to center shaft 110.

Rear endplate 122 carries and locates rear bearing 124, mounts andlocates stator core 328, and suitably provides a mounting surface forfan 126. Rear endplate 122 suitably includes a stepped central hub 340having a forward reduced diameter portion 342 and central aperture 344there through, and a generally cylindrical rearward going outer portion346, preferably having the same outer diameter as front endplate 116,connected to hub 340 by respective crossarms 348. As will be furtherdescribed, rear endplate 122 also suitably includes respective airpassageways 347, bounded by adjacent crossarms 348, outer portion 346,and hub 340. Respective through bores 350 are provided cylindrical outerportion 346, at the same radial distance from center and angulardispositions as tapped holes 337 in front endplate 116. A predeterminednumber of tapped holes (e.g. 4) corresponding to stator crossarm bores410 (or mounting collar bores 416) are provided in the stepped surfaceof projection 340. The outer diameter of reduced diameter portion 342 issubstantially equal to (but slightly less than) the diameter of statoraperture 406, so that rear endplate portion 342 may be closely receivedwithin stator aperture 406. Rear endplate 122 is dimensioned andmachined to high tolerance (e.g. plus or minus 0.0008 TYP for centralaperture 344, 0.005 TYP for other features, such as tie rod hole 350patterns, outer case shoulder, mounting hole patterns), suitably formedof metal e.g. cast aluminum. Rear bearing 124 is closely received withinaperture 344 of rear endplate hub 340 and thus centers shaft 110.

Stator core 328 is mounted on hub 340, with reduced diameter hub portion342 received within stator aperture 406 and the stator rear sidewallabutted against the hub step. If core 328 includes crossarms 408, thecrossarms suitably abut hub 340. If core 328 does not include crossarms408, e.g., skewed core 329, the core interior surface 407 suitably abutsreduced diameter hub portion 342. Respective bolts 352 journaled throughbores 410 (or 416) and secured in tapped holes 350, secure stator core328 to rear endplate 122. Stator 114 is thus positively located andaligned relative to shaft 110.

In accordance with one aspect of the present invention, rotor 112 ispositively located on and aligned with shaft 110. More specifically, aspreviously noted, includes a portion 310 with a predetermined taper(e.g. suitably in the range of 1 in. diameter per 7 inches of length to1 in. diameter per 16 inches of length, and preferably 1 in. per foot.),just forward of threaded portion 134, between front bearing 118 and rearbearing 124. The minimum diameter of shaft tapered portion 310 issuitably slightly greater then the diameter of threaded portion 134.Rotor hub 324 includes a through-bore 326 having a predetermined tapercorresponding to that of shaft portion 310. The maximum diameter oftapered through bore 326 corresponds to (e.g. is substantially equal toor slightly less than) the maximum diameter of shaft of tapered portion310, and the minimum diameter of tapered through bore 326 corresponds to(e.g. is substantially equal to or slightly smaller than) the minimumdiameter of shaft of tapered portion 310. The axial dimension of hub 324is such that when fully seated, it extends slightly beyond the end ofshaft section 310 axial dimension of hub 324 is such that when fullyseated, it extends slightly beyond the end of shaft section 310. Inassembly, shaft 110 is journaled through bore 326, such that shafttapered portion 310 is received in bore 326. Threaded shaft portion 312cooperates with jam nut 120 to force rotor hub tapered surface 326axially into wiping contact with the tapered surface of shaft portion132 until the surfaces mate. Rotor 112 is thus accurately positioned,centered and aligned on shaft 110 with a strong mechanical bond.

Since endplates 116 and 122 are held in alignment with each other byouter casing 128 and tie rods 130, shaft 110 (and tapered portion 310)is held in alignment with endplates 116 and 122 by bearings 118 and 124,and stator 114 is positively positioned and aligned with shaft 110 byendplate 122, the positive positioning and a centering of rotor 112 onshaft 110 also provides relative positioning and alignment between rotor112 and stator 114.

In vehicular applications alternator 110 may be subjected to relativelysevere accelerations that tend to cause distortion and/or displacementof rotor 112 due to the moment of inertia inherent in the rotationalcase. Such accelerations are, due to, for example, engine vibration(particularly diesel engines at startup), cornering, traversing bumpyroads or terrain, and other types of impact. The efficiency of permanentmagnet alternator 100 is inversely proportional to the width of “airgap” 412 separating the magnets from the stator. As previously noted,air gap 412 is suitably in the range of 20 to 40 thousands of an inch,and in the embodiments of FIGS. 1-4 on the order of 30 thousands of aninch, e.g., 31 thousands of an inch. Displacement of rotor 112 need onlyexceed the width of air gap 412 to clause clashing and possiblydestructive interference. Further, for a variety of reasons, e.g. tominimize inertia in operation of alternator 100, it is desirable thatrotor 112 be as light as possible. Accordingly, rotor 112 tends to besusceptible to distortion due to such forces.

Referring to FIG. 5A, in the absence of external forces, rotor 112 isconcentric and perpendicular with shaft 110; rotor casing 316 is in anominal normal position (designated by lines 502 and 504) coaxial withshaft 110 and the forward (closest to forward endplate 116) edge ofrotor endcap 314 is in a nominal normal position (designated by line506) perpendicular to the axis of shaft 110. Components of externalforces typically encountered parallel to the axis of shaft 110 tend tohave little effect on the disposition of rotor 112; rotor endcap 314 andcooperation of rotor hub 324, tapered shaft portion 310, and jam nut 120are sufficiently strong to resist axial movement or distortion of rotor112, and, in any event, there is greater tolerance to axial distortions.However, external forces tend to be encountered with componentsperpendicular to the axis of shaft 110 of sufficient strength to distortrotor 112. In addition to deflection of rotor 112 due to externalforces, as a practical matter, due to limitations (tolerances) in themanufacturing process, rotor 112 tends to be very slightly out of round(cylinder casing 316 will not be absolutely parallel to shaft 110),causing a conical wobble during rotation further reducing the air gapeccentrically.

More specifically, when subjected to accelerations perpendicular to theaxis of shaft 110, rotor casing 316 tends to maintain its cylindricalshape. However, a distortion is manifested in rotor endcap 314. Ineffect, rotor 112 is cantilevered at the conjunction of rotor endcap 314and shaft 110 (indicated a schematically as anchor (cantilever) point508). In response to perpendicular acceleration, rotor 112, in effect,pivots about anchor point 508 in the direction of the force. Maximumdeflection from the nominal normal position is experienced at theportions of rotor 112 farthest from anchor point 508, i.e. the distal(rear) end of casing 316, and the outer periphery of endcap 314 (whereendcap 314 joins casing 316). If the deflection in the vicinity ofmagnets 318 exceeds air gap 412, e.g. 31 thousands of an inch, magnets318 will clash with stator 114, causing possibly destructiveinterference. Similar issues arise if out of round wobble causes adeviation from the norm that exceeds air gap 412.

For example, as shown in FIG. 5B, in response to an upward acceleration,rotor 112 will in effect pivot downwardly (as shown, in a clockwisedirection). The upward side of rotor casing 316 will effectively pivotinwardly towards shaft 110, with the distal end deflected inwardly fromthe nominal normal position 502 by an amount generally indicated as 510.The upward periphery of endcap 314 similarly moves to the rear of itsnominal normal position 506 by an amount generally indicated as 512.Conversely, the distal end of downward side of rotor casing 316 will bedeflected outwardly from the nominal normal position 502 by an amountgenerally indicated as 514 and the downward periphery of endcap 314similarly moves forward of its nominal normal position 506 by an amountgenerally indicated as 516. Since cylindrical rotor casing 316 maintainsits shape, the amount of deflection of the corresponding upper and lowerportions are substantially proportional i.e. deflections 510 and 512 aresubstantially proportional (and in many geometries equal) to deflections514 and 516, respectively.

Forces from opposite directions will cause mirror image deflections. Forexample, as shown in FIG. 5C, in response to a downward acceleration,rotor 112 will in effect pivot upwardly (as shown, in a counterclockwisedirection). The downward side of rotor casing 316 will effectively pivotinwardly towards shaft 110, with the distal end deflected inwardly fromthe nominal normal position 504 by an amount generally indicated as 518.The downward periphery of endcap 314 similarly moves to the rear of itsnominal normal position 506 by an amount generally indicated as 520.Conversely, the distal end of upward side of rotor casing 316 will bedeflected outwardly from the nominal normal position 502 by an amountgenerally indicated as 522 and the upward periphery of endcap 314similarly moves forward of its nominal normal position 506 by an amountgenerally indicated as 524. Again, since cylindrical rotor casing 316maintains its shape, the amount of deflection of the corresponding upperand lower portions are substantially proportional (and in manygeometries equal) i.e. deflections 518 and 520 are substantiallyproportional essays to deflections 522 and 524, respectively.

In accordance with a further aspect of the present invention, clashingis prevented by disposing one or more bumpers to arrest rotor deflectionfrom the nominal normal position before the deflection of magnets 318exceeds air gap 412. The bumpers can be disposed on either or both ofthe interior or exterior of rotor 112, interacting with one or both ofcasing 316 or end cap 314; since rotor casing 316 maintains its shapepreventing either inward or outward deflection of casing 316 or end 314from exceeding predetermined limits corresponding to the width of theair gap will prevent clashing. Bumpers are formed of a relatively smoothand resilient material with a predetermined durometer such that itdeforms no more than a predetermined amount before arresting deflectionof rotor 112 in response to maximum loads (e.g. 20 g's gravities).Examples of such a material are Teflon, glass impregnated Teflon and oilimpregnated sintered bronze. The bumpers can be disposed on, forexample, a feature of rear endplate 122, front endplate 116 or othersupport structure (e.g. tie rods 130), and use a portion of rotor 112 asa bearing surface. Alternatively, the bumper can be disposed on rotor112 and utilize a feature of the support structure as a bearing surface,or in some instances be interposed in air gap 412 between magnets 318and stator 114. The bumpers are disposed separated from the cooperatingbearing surface by a predetermined amount, sometimes referred to hereinas a “support gap”, e.g. 0.01 in. The support gap is chosen such thatthe support gap plus the maximum amount of deformation of the bumper isless than magnetic air gap 412. In addition the bearing surfacesinteracting with the bumper may be treated, e.g. to minimize frictionand/or hardened. For example, chrome or some other type metallic zinctype finish may be employed.

As previously noted, clashing of magnets 318 and stator 114 can beavoided by preventing inward deflection of rotor casing 316. Referringto FIGS. 6A and 8, a generally cylindrical shoulder 602 may be formed onrear endcap 122, extending forward to underlie the end of rotor casing316, i.e. received within rotor internal chamber 320. The outer diameterof shoulder 602 is less than the inner diameter of rotor casing 316 by apredetermined amount. A cylindrical bumper 604 is disposed aboutshoulder 602. The outer surface of bumper 604 is thus coaxial with rotorcasing 316, and separated from the inner surface of rotor casing 316 bya support gap 606. Bumper 604 is formed of a material with apredetermined durometer such that it deforms no more than apredetermined amount before arresting deflection of rotor casing 316.Support gap 606 is chosen to be sufficiently less than magnetic air gap412, that the inner surface of rotor casing 316 overlying bumper 604comes into contact with bumper 604 and maximum deformation of bumper 604occurs before magnets 318 come into contact with stator core 314, i.e.the support gap plus the maximum amount of deformation of bumper 604 isless than magnetic air gap 412. If desired, a surface treatment, e.g. achrome, metallic zinc or hard anodize layer 608 can be provided on thebearing surface of rotor casing 316.

Alternatively, as shown in FIG. 6B, a cylindrical bumper 610, havingouter diameter substantially equal to the inner diameter of rotor casing316, can be affixed (e.g. glued) to the inner surface of rotor casing316. The inner surface of bumper 604A would be separated from the outersurface of rear end shoulder 602 (which acts as the bearing surface) bysupport gap 606. If desired, a surface treatment 608A can be provided onthe bearing surface of shoulder 602.

In some applications it may be desirable to employ a bumper (or surfacetreatment) in the form of a collar or sleeve received about the mouth ofrotor casing 316. An example of such a structure is shown in FIG. 6C. Acollar bumper 612 having a cylindrical body 614 of predetermined lengthand thickness and a lip 616 is affixed (e.g. glued by, for example,epoxy) to the mouth of rotor casing 316. Collar bumper 612 cooperateswith rear endplate 122 to prevent clashing of magnets 318 and stator114. Collar body 614 is separated from the sidewall of shoulder 602(which acts as a bearing surface with respect to collar body 614) by asupport gap 606. If desired, the end surface of collar lip 616 maycooperate with the sidewall of rear endplate 122 separated from rearendplate 122 by an appropriate support gap 606A to provide additionalprotection against deflection of rotor casing 316.

In general, it is desirable to dispose as little as possible on rotor112 to minimize rotor weight, and thus inertia. In some instances,however, ease of assembly may make the embodiments of FIG. 6B or 6Cdesirable.

As previously above, clashing of magnets 318 and stator 114 can beavoided by preventing outward deflection of rotor casing 316. Referringto FIGS. 6D and 8, a generally cylindrical shoulder 618, coaxial withrotor casing 316 but having an inner diameter greater than the outerdiameter of rotor casing 316 by predetermined amount, is provided onrear endcap 122, extending forward to overlie the end of rotor casing316. A cylindrical bumper 620, is affixed (e.g. glued) to the interiorsidewall of shoulder 618, positioned coaxial with rotor casing 316. Theinner diameter of bumper 620 is greater than the outer diameter of rotorcasing 316 by an amount equal to a support gap 622. The outer surface ofrotor casing 316 acts as a bearing surface. If desired, a surfacetreatment 608B can be provided on the bearing surface of rotor casing316.

Bumpers can be disposed on other support structure, and use a portion ofrotor 112 as a bearing surface. For example, referring to FIGS. 6E and8, respective cylindrical bumper sleeves 624 are disposed coaxially oneor more (preferably each) of tie rods 130. The outer diameters of bumpersleeves 624 are chosen such that the surface of the sleeve nearest rotorcasing 316 is separated from casing 316 by an appropriate support gap626. Bumper sleeves 624 may be affixed to tie rods 130, but arepreferably rotatable, i.e. act as rollers with tie rods 130 as axes.Rotation of bumper sleeves 624 will tend to reduce wear, and extend thelife of the bumpers. Disposition of bumper sleeves 624 at least two setsof opposing tie rods 130 (at 180° from each other) around rotor casing316 tends to counteract forces on rotor 112 from any directiontransverse to shaft 110.

Bumpers may also be disposed on front endplate 116, with the frontsurface of rotor endcap 314. Referring to FIGS. 6F and 8, a annularbumper 628, is affixed (e.g. glued) to the interior sidewall of frontendplate 116, positioned coaxial with rotor casing 316. The inner andouter diameters of bumper 628 are preferably chosen to correspond to(e.g. bracket) the outer periphery of endcap 314. A annular depression630 for receiving and locating bumper 628 is suitably provided in theinterior sidewall of front endplate 116. If desired, other locatingfeatures (e.g. projections or a shoulder) may also be provided on theinterior sidewall of front endplate 116 to position bumper 628. Suchprojections, however, are suitably lower in profile than the maximumdeflection of bumper 628. The thickness of bumper 628 is chosen suchthat the face opposing rotor endcap 314 is separated from endcap 314 byan appropriate support gap 632. The forward surface (closest to frontendplate 116) of rotor endcap 314 acts as a bearing surface. By limitingthe extent that the forward (closest to forward endplate 116) edge ofrotor endcap 314 from its nominal normal position, clashing of magnets318 and stator 114 can be averted. If desired, a surface treatment 608Bcan be provided on the bearing surface of rotor endcap 314.

In some instances (e.g. in the case of bumper sleeves 622) it may bedesirable to initially place bumper 604 in contact with the bearingsurface i.e. establish an initial support gap of zero. In such cases thematerial of the bumpers would-be chosen such that relative motion andinteraction between the bearing surface and the bumpers would abrade thebumpers to ultimately establish an appropriate support gap.

In some instances, it may be desirable to interpose a thin band ofbumper material in air gap 412 between magnets 318 and stator 114. Forexample, referring to FIGS. 6G and 8, a thin band 634 of relativelyrobust substantially magnetically transparent material (e.g. Teflontape) is disposed within air gap 412 on the outer surface (crenellatedcylindrical sidewall) of stator 114 along the rear edge (edge of nearestrear endplate 122). Band 634 is made of a material having a durometersufficient, given the thickness of band 634, to avoid total compressionunder maximum load and prevent magnets 318 from impact with stator 114.In addition, it is desirable that band 634 exhibits a relatively lowcoefficient of friction. If desired, a chromium surface treatment can beapplied to magnets 318 to further reduce friction.

In addition to preventing potential clashes by using bumpers to limitthe extent that rotor 112 can be deflected from its nominal normalposition. It is also desirable to minimize the effect of external forcesand out of round conditions due to manufacturing tolerances.

In accordance with another aspect of the present invention, deflectionof rotor casing 316 (magnets 318) from the nominal normal position inresponse to force components perpendicular to shaft 110, and wobble dueto out of round components can be reduced by reducing the axial distancebetween magnets 318 and the anchor point. This is achieved while stillproviding sufficient space in internal cavity 320 for stator windings330, by contouring endcap 314 to couple the forward most end of rotorcasing 316 (nearest front endplate 116) to an anchor point closer tomagnets 318 within the interior of casing 316. At least a portion ofrotor endcap 314 (e.g. crossarms 322) would effectively be at an angleother than 90° relative to rotor casing 316 (and hence shaft 110). Theangled portion could be straight (e.g. such that a portion of endcap 314was generally conical) or curved (e.g. such that a portion of endcap 314was generally bell-shaped).

As previously noted, rotor 112 is, in effect, cantilevered at theconjunction of rotor endcap 314 and shaft 110 (anchor point 508 in FIG.5). Maximum deflection from the nominal normal position due to externalforces occurs at the portions of rotor 112 farthest from the anchorpoint, i.e. the distal (rear) end of casing 316, and the outer peripheryof endcap 314 (where endcap 314 joins casing 316). Similarly, thegreatest deviation from the normal path due to out of round wobbleoccurs at the portions of rotor 112 farthest from the anchor point, i.e.the distal (rear) end of casing 316. Out of round conditions due totolerances result in a conical displacement from the nominal position ofcasing 316 i.e. as rotor 112 rotates around a given point on stator 114,rotor casing 316 will approach, and retreat from that point on stator114. The greater the axial distance of the point on stator from thepivot point the greater the relative motion of the casing 316. Forexample, as shown in FIGS. 7A and 7B, at an axial distance X1 from thepivot point (e.g. the axial distance from pivot point 508 of a “flat”hub to the rear end of rotor casing 316), out of round conditions due totolerances will tend to cause a wobble toward and away from the statorin the amount W1. However, at a lesser distance X2 (e.g. the axialdistance from pivot point 708 of a conical hub to the rear end of rotorcasing 316), a lesser amount W2 is experienced. Accordingly, by movingthe anchor point closer to the rear end of rotor casing 316 (and magnets318), wobble in the vicinity of magnets 318 and stator 114 is reduced.

Referring to FIG. 7A, reduced wobble rotor 712 includes an endcap 714having a hub 724 that establishes an anchor (cantilever) point 708disposed within the interior of rotor casing 316. Anchor point 708 isrearwardly displaced along the axis of shaft 110 from the forward edgeof casing 316 (nearest front endplate 116), by a predetermined distanceD1. In typical automotive applications, the diameter of casing 316 issuitably in the range of 2½ to 5 in., and preferably 4½ inches; and thelength of casing 316 is suitably in the range of 3 to 6 in., andpreferably 5 in. Distance D1 is suitably in the range of ½ to 1 inch andpreferably ¾ inch. In certain military and commercial vehicles (e.g.Hummers), the diameter of casing 316 is suitably in the range of 5 to 8in., and preferably 6½ inches; and the length of casing 316 is suitablyin the range of five ½ to 10 in., and preferably 7 in. Distance D1 issuitably in the range of ¾ to 2 inch and preferably 1½ inch.

Rotor endcap 714 is contoured to connect the forward end of casing 316to hub 724, while at the same time providing sufficient space ininterior cavity 320 to accommodate stator windings 330. For example, inthe embodiment of FIG. 7A, endcap 714 comprises a conical portion 726(which may include a plurality of apertures (e.g. 3) to, in effect,provide prospective angled cross arms) , and a generally annularperipheral portion 728 connecting cross arms 722 to the forward end ofcasing 316. Peripheral portion 728 extends perpendicularly from casing316 towards shaft 110 a predetermined distance, suitably in the range of½ inch to 2 inches, and preferably ¾ inches. Internal chamber 320 thusextends farther forward in the vicinity of the crenellated outer edge ofstator core 328, and windings 330.

FIG. 7C shows a hub similar to that shown in FIG. 7A except thatexternal surface 729 meets shaft 110 perpendicularly greatly increasingthe cross sectional area. This increases the strength of endcap 714helping it to better resist deflection as outlined in FIG. 5. In FIG. 7Ccasing 316 is welded 731 to endcap 714.

FIG. 7D shows both endcap 714 and casing 316 formed as a single integralunit 732. Unit 732 is suitably cast then machined, further increasingits strength. Unit 732 can also be machined entirely from a singlebillet of e.g., steel.

FIG. 7E shows all three, endcap 714, casing 316 and shaft 110 casts thenmachined as a single unit 733. This configuration allows for maximizedstrength and alignment since both the shaft portion and inner casingwill be machined together minimizing wobble. This configuration also hasthe benefit of reducing parts and assembly time. Unit 733 can also bemachined entirely from a single billet of steel eliminating the need fora casting.

As shown schematically in FIG. 8, a variety of bumpers can be used incombination, together with a contoured rotor endcap.

As previously noted, the heat generated by compact high poweralternators can also be problematical. The stator windings are formed ofa suitably insulated electrical conductor, e.g. varnished copper motorwire, and are wound through respective slots and about a predeterminednumber of teeth in the periphery of the stator core. As the rotorrotates relative to the stator, the magnetic field generated by therotor magnets interacts with the windings, causing an electrical currentto be generated. The windings, however, have a characteristic, andcurrent flow through the windings generates heat that must bedissipated. Conventionally, the windings are tightly wound about thestator core, to minimize the length of the windings, and henceimpedance, and airflow to effect cooling has been provided by fansdriven by the motive force to the rotor, e.g. off of the shaft on whichthe rotor is attached. Accordingly, little airflow is provided at lowrpm.

However, in various automotive applications, such as, for example,hybrid vehicles, demand for relatively high levels of power, and thus anelevated need for cooling, can occur at low rpm, e.g. at idle speeds.This is also particularly true in those instances when astarter-generator or other electric motor is employed to provide aninitial burst of propulsion when the driver depresses the acceleratorpedal, facilitating shutting off the vehicle engine when the vehicle isstopped in traffic to save fuel and cut down on emissions. Further, incompact high power alternators, significant heat levels are generated ina relatively small area. The efficacy of air cooling of alternatorcomponents is a function of the quantity of air flowing through thealternator. The in compact high power alternators the cross-sectionalarea available for airflow for a given power output is less than thatavailable in a conventional alternator. Accordingly, air cooling tendsto be less efficient. However, permanent magnets are particularlysusceptible to damage due to overheating; under high load, hightemperature conditions, such magnets can become demagnetized. Similarly,the electronic components employed in the controller are susceptible toheat damage. Thus, conventional cooling techniques tend to be inadequatefor such compact high power alternators, particularly in automotiveapplications.

In accordance with other aspects of the present invention, cooling isfacilitated by one or more of: loosely wrapping winding end turns 332to, in effect, increase the surface area of windings 330; establishing adirected airflow over at least a portion the stator windings,(preferably through loosely wrapped end turns of the windings);directing a portion of the airflow over elements in thermal contact withmagnets 318 (e.g. over rotor casing 316) to cool magnets 318; providingairflow from a source that is asynchronous with respect to the shaft onwhich the rotor is mounted, e.g. an electric fan: and directing a flowof coolant fluid into thermal contact with end turns 332 (preferablythrough thermally conductive conduits including one or more portionsdisposed in loops generally concentric with the stator core in thermalcontact with front end turns 332A and/or rear end turns 332B).

As previously noted in conjunction with FIGS. 3 and 4, windings 330 arewound through a respective slot 404, outwardly along the side face ofcore 328 around a predetermined number of teeth 402 forming an end turn332, then back through another slot 404. More particularly, withreference to FIGS. 9A, 10A and 10B, each of windings 330 comprises atleast one associated bundle of individual strands of insulatedconductive wire (e.g. varnished copper motor wire) In contradistinctionto the conventional practice, end turns 332 are loosely wrapped aroundthe side faces of the stator core, with air spaces between the variousbundles and the core side face, (rather than drawing the winding endturns tightly against the side face of the stator core to minimize costand impedance). The inefficiencies inherent in loosely extending thewinding end turn beyond the stator has been determined to beinsignificant in comparison to the increased cooling capacity providedby exposed surface areas of the open winding structure. Preferably, asbest seen in FIG. 10A, respective end turns 332 extend varying distancesfrom stator side face 328, presenting a lattice-like structure to theairflow. End turns 332 suitably extend distances from stator side face328, ranging from 0 to 1½ inch, and preferably from ¼ to 1 in. Forexample, adjacent end turns would extend outwardly by incrementallydifferent distances e.g. increments of one half-inch to progressivelyfan out from the stator. In the embodiment of FIG. 10, a first end turn1002 is offset from stator side face 328 by approximately a firstpredetermined distance, e.g. ½ inch. The next adjacent end turn 1004 isoffset from stator side face 328 by approximately an incrementallyincreased distance, e.g. ¾ inch. Likewise, the next adjacent end turn1006 is offset from stator side face 328 by approximately a furtherincrementally increased distance, e.g. 1 inch. The pattern is thensuitably repeated. This arrangement is equally valid for a skewed core329 as shown in FIG. 10B.

If desired, the lattice pattern can be established by offsettingrespective end turns 332 associated with each phase a different offsetdistance from stator side face 328; for a three-phase system, the endturns of phases A, B, and C, suitably have offset distances ofapproximately ½ in., ¾ in., and 1 in., respectively.

Referring to FIG. 9A, a cooling airflow is directed over stator windings330 (preferably through loosely wrapped front-side and rear-side endturns 332A and 332B) by employing a cooling system comprising airpassageways 902 in rear end plate 122 (bounded by adjacent rear endplate crossarms 348, outer portion 346, and hub 340), stator centralaperture 406, rotor air passages 323 and front end plate air passages136. Air exiting rear end plate air passage way 902 is directed toimpinge on windings 330 (rear-side end turns 332B), by virtue ofsuitable relative disposition or contouring, or, as in the embodiment ofFIG. 9A, cooperation with a rear deflector 904. Similarly, air exitingstator central aperture 406 is directed to impinge on windings 330(front-side end turns 332A), by virtue of suitable relative dispositionor contouring, or, as in the embodiment of FIG. 9A, cooperation with afront deflector 906. An asynchronous forced air supply, e.g., electricfan 126, mounted on the back of rear end plate 122 is preferablyutilized. In the preferred embodiment, a conventional fan 908 is alsomounted for rotation with shaft 110 between pulley 132 and front endplate 116. The cross sections, contours (turns and edges) and relativedispositions of the various air passageways are preferably chosen tominimize decreases in air velocity, and maximize airflow over end turns332.

More specifically, cooling air, generally indicated by arrows 910(preferably forced air from asynchronous fan 126) is introduced intoalternator 100 through end plate air passageways 902. Airflow 910impinges upon rear deflector 904, and is redirected in a radiallyoutward direction; air that would otherwise flow through stator centralaperture 406 flows outward and about stator core 328. In the preferredembodiment, the outwardly redirected air impinges upon and flows throughthe spaces between rear-side loosely wrapped rear-side end turns 332B ofwindings 330. Airflow 910 then splits into respective streams 914 and916. After exiting the end turns 332B, air stream 914 flows throughstator central aperture 406, impinges upon front deflector 906, isdirected through the front-side loosely wrapped end turns 332A, rotorpassageways 323 and then exits alternator 100 through air passageways136 in front end plate 116 . Air stream 914 comprises the bulk ofairflow 910, since stator central aperture 406 represents the largestdiameter path, and hence the path of least resistance. Air stream 916,after exiting rear-side end turns 332B, flows around the outside ofrotor casing 316, then exits alternator 100 through air passageways 136in front end plate 116. Air stream 916 provides cooling of magnets 318.

Rear deflector 904 comprises an element presenting a predeterminedcontour to the impinging air stream 910 to redirect the air stream ontowindings 330 (preferably rear-side end turns 332B) to dissipate heatgenerated in windings 330. The diameter and predetermined contour of thereflector 904 is chosen effectively redirect the air as much as possiblethrough the windings without creating too a large a decrease in airvelocity. Rear deflector 904 is suitably a generally conical or dishshaped element with a central aperture, concentrically disposed on rearend plate hub 340, disposed with the apex facing into the airflow. Reardeflector 904 extends radially outward into the path of air stream 910as it exits rear end plate air passageway 902, preferably at or justunder the outer periphery of stator central aperture 406. Rear deflector904 may be formed of any suitable relatively rigid material, such as,e.g., sheet metal, or plastic, or may be formed integrally with rear endplate 122. The choice between use of a separate deflector component, ora deflector feature integrally formed in end plate 122 is primarily anissue of cost.

Front deflector 906 likewise suitably comprises an element presenting apredetermined contour to the impinging air stream 914 to redirect theair stream onto windings 330 (preferably front-side end turns 332A) todissipate heat generated in windings 330. The diameter and predeterminedcontour of deflector 906 is chosen effectively redirect the air as muchas possible through the windings without creating too a large a decreasein air velocity. Deflector 906 suitably comprises a generally conical ordish shaped element with a central aperture, disposed with the apexfacing into the airflow. Front deflector 906 is concentric with rotorhub 324 (shaft 110), suitably rotates with rotor 112, and extendsradially outward into the path of air stream 914 exiting stator centralaperture 406. Front deflector 906 may be formed of any suitablerelatively rigid material, such as, e.g., sheet metal, or plastic, ormay be formed integrally with rotor 112 or jam nut 120. The choicebetween use of a separate deflector component, or a deflector featureintegrally formed in rotor 112 or jam nut 120 is primarily an issue ofcost. In the embodiment of FIG. 9A, front deflector 906 suitably has anouter diameter such that the outer periphery extends approximately ¾ ofthe way into stator central aperture 406.

If desired, in addition to (or in some instances in lieu of) deflectors906 and 904, heat transfer efficiency can be increased by bending endturns 332 into the air stream. More particularly, referring to FIG. 11,end turns 332 are bent inwardly beyond the periphery of stator centralaperture 406, and into the path of air flowing through the aperture.

As previously noted, in the embodiment of FIG. 9A, a conventionalsynchronous fan 908 is mounted for rotation with shaft 110 betweenpulley 132 and front end plate 116. Fan 908 in effect, creates a vacuumthat pulls air through alternator 100. However, alternator 100 iscapable of generating high levels of power at idle, or just above idle,speeds. Fan 908, rotating synchronously with shaft 110, is typicallyunable to provide sufficient airflow for cooling under such conditions.Electric fan 126, which operates a synchronously from shaft 110,suitably provides an auxiliary cooling, providing a positive pressure topush air through alternator 100.

Fan 126 is, as previously noted, mounted on the back of rear endplate122. In general, it is desirable to maximize airflow through alternator100. Accordingly, fan 126 is preferably chosen to provide the largestcubic feet per minute (CFM) zero pressure given the size constraints ofalternator 100. Commercially available fans can be employed. However,preferably fan 126 is a permanent magnet fan, with a blade diameterapproaching that of alternator outer casing 128.

The use of fluids for cooling in addition to, or in lieu of, forced aircan be advantageous under operating conditions of low airflow, orextreme heat and, in sandy, wet, or otherwise harsh conditions.

For example, in some cases it is advantageous to supplement air coolingwith fluid cooling of coil end turns 332. In general, a coolant fluid isdirected into thermal contact with end turns 332 while maintainingelectrical isolation. For example, coolant fluid can be routed throughthermally conductive conduits including one or more portions disposed inthermal contact with front end turns 332A and/or rear end turns 332B.The conduit portions suitably track the shape of end turns 332, e.g.,comprise generally circular or helical loops generally concentric withthe stator core disposed proximate to the end turns. The conduits can beformed of any thermally conductive material that is capable ofwithstanding the elevated temperatures found in the alternator andnonreactive with the chosen coolant. Suitable materials include, forexample, copper, and aluminum tubing. The conduit is preferablythermally connected to the adjacent end turns by an electricallyinsulating heat conductor, such as, for example, engineered epoxy. Thecoolant fluid can be any fluid, preferably liquid, having suitablethermal and flow characteristics. One example is conventional enginecoolant. In vehicular applications, the engine coolant would preferablybe directed into the alternator immediately after exiting the radiator.

Referring to FIGS. 9B and 9E, in a preferred embodiment, a coolant fluidis directed into thermal contact with end turns 332 through a conduit(e.g., copper tubing) 918. Conduit 918 suitably includes an inlet 922,axially directed portions 950, 958 and 966, radially directed portions952, 956, 960, and 964, and looped portions 954 and 962. Looped portions954 and 962 each suitably comprises one or more circular or helicalturns centered about the axis of stator core 328, with diameter(s)corresponding to the annulus formed by end turns 332 (e.g., bounded bythe bottom of slots 404 and the outer perimeter of core 328). Conduitportions 952, 954 and 956 are suitably all disposed in a planeperpendicular to the axis of stator core 328, (parallel to the frontface) just in front of front end turns 332A. Conduit portions 960, 962and 964 are likewise suitably all disposed in a plane perpendicular tothe axis of stator core 328, (parallel to the back face) just behindrear end turns 332B. Axial portions 950 and 958 suitably extend throughstator central aperture 406. Axial portions 950 and 966 suitably extendthrough rear endplate inner passageway 902. Coolant is introduced atinlet 922, and then flows through portions 950, 952, 954, 956, 958, 960,962, 964, and 966, in sequence, then exits through an outlet 924.

Conduit 918 is thermally connected to end turns 332 by an electricallyinsulating, thermally conductive material 920 (e.g. engineered epoxy).Material 920 suitably encapsulates end turns 332, looped portions 954and 962, and a part of radial portions 952, 956, 960 and 964. Material920 conducts heat from end turns 332 to the coolant, while at the sametime providing electrical isolation.

In the embodiment of FIG. 9B, magnets 318 are cooled using air stream916. Air stream 916 flows around the outside of rotor casing 316, thenexits alternator 100 through air passageways 136 in front end plate 116.The air flow is supplied by fan 908. An asynchronous fan 126 as shown inFIG. 9A can be used to enhance the cooling of magnets 318.

If desired, the coolant flow through conduit 918 can also be used tocool magnets 318 to permit an essentially closed system. An airflow,cooled by the coolant flow through conduit 918, is directed acrossmagnets 318.

Referring to FIGS. 9C and 9D, respective thermally conductive heatexchange fins 922 are provided, thermally connected to the conduit 918.Fins 922 are suitably incorporated into thermally conductive encapsulant920. Fins 922 suitably extend radially into central aperture 406.

Respective blades are disposed on the forward face of rotor 112 to forma centrifugal fan 926. Fan 926 generates an airflow 916; air is drawnthrough stator core central aperture 406, over heat exchange fins 922,through apertures 323 in the end plate of rotor 112, and forced to flowaround the outside of rotor casing 316. The airflow, after flowingaround the outside of rotor casing 316, is directed by passageway 928back into central aperture 406. The airflow around the outside of rotorcasing 316 carries the heat created by magnets 318 across the heatexchanger fins 922 embedded in encapsulant 920. Fluid coolant flowing incooling tubes 918 thus carries away heat generated by both the windingsof stator 328 and magnets 318.

Since the need for air circulation from an outside source is no longrequired, the alternator is suitably sealed using o-rings 930 and plugs932. This has the advantage of sealing out most if not all contaminationdetrimental to the operation of a permanent magnet alternator. Ifdesired, a one-way valve or membrane (not shown) located at the lowestpoint of the alternator can be provided to assist in draining possibleaccumulation of water. In the event a greater air flow is required, anasynchronous fan 126 can be installed.

Under some circumstances, e.g., in sandy, wet, or otherwise harshconditions, an air cooled alternator can be sealed with respect topotential external contaminants. In accordance with another aspect ofthe present invention, a sealed air cooled alternator is provided byestablishing separate internal and external cooling airflows over anexternal alternator case acting as a heat exchanger. The internal andexternal airflows are suitably provided by internal and external fans.The internal airflow is directed over the stator coils, rotor andinterior of the heat exchanger to transfer heat from the coils andmagnets to the heat exchanger. The exterior airflow is directed over theexterior of the exchanger to dissipate the heat. If desired, the sourcefor the external airflow can be remotely located from the alternator,e.g., provided through plenums or snorkels.

Referring to FIG. 12, a first embodiment of a sealed alternator 1200comprises: shaft 110; a sealed front end plate 1202; front bearings 118;stator 114; a forward facing rotor 1204; jam nut 120; an internal fan1206; rear bearing 124; a sealed rear endplate 1208; a heat exchanger1210; an external fan 1212 and a fan housing 1213 with an air intake1214. (In this embodiment, tie rods 130 (not shown) may be disposedexternally, as illustrated in FIG. 4) Front end plate 1202 suitablyincludes a stepped central hub 1214 (generally analogous to rearendplate hub 340 in the embodiment of FIG. 3) for mounting and locatingfront bearing 118, and stator core 328. Tapered portion 310 of shaft 110is disposed at a predetermined axial distance from front end plate 1202(generally corresponding to the axial length of rotor 1204). Rotor 1204is essentially the same as rotor 112, but with the tapered portion ofhub 324 reversed to accommodate a forward facing disposition of rotor112. As in the embodiment of FIG. 3, rotor 1204 is mounted for rotationon shaft 110, positively located on and aligned with shaft 110 bycooperation of hub 324 with shaft tapered portion 310, and stator 114 isclosely received within rotor 1204, separated from rotor 1204 by a smallair gap 412. Heat exchanger 1210 is generally cylindrical and disposedcoaxially with shaft 110, exteriorly of rotor casing 316. Front endplate 1202, bearings 118 and 124, heat exchanger 1210 and rear endplate1208 provide a sealed compartment enclosing stator 114, rotor 1204 andinternal fan 1206.

Referring to FIGS. 12 and 13A, heat exchanger 1210 suitably comprises acylindrical separator (casing) 1216 and bearing radially extendinginternal and external fins, 1218 and 1220 respectively, all in thermalcontact. Heat exchanger 1210 is suitably a unitary extrusion ofthermally conductive material, such as aluminum or steel. Alternatively,as shown in FIG. 13B, for ease of construction, heat exchanger 1210 canbe formed of a separate cylindrical casing formed of a first material,e.g., steel, with a plurality (e.g. 12, only one shown) of separate(suitably extruded) fin sections 1218A (each extending over apredetermined arc) formed of a second material, e.g. aluminum, coveringthe interior face of cylinder 1216 and a plurality (e.g. 12, only oneshown) of separate (suitably extruded) fin sections 1220A covering theexterior face of cylinder 1216. For example, twelve 30° sections of finsor four 90° sections of fins can be employed. The respective finsections 1216A and 1220A are fixed on, and in thermal contact with,casing 1216, suitably by an adhesive (that remains sufficiently flexibleto accommodate the different rates of thermal expansion of the first andsecond materials).

Heat exchanger 1210 is disposed coaxially with and radially outward fromrotor casing 316. Respective axial channels 1226 are defined betweenadjacent internal fins 1218, casing 1216 and the outer surface of rotorcasing 316. As will be explained, airflow through channels 1226 transferheat from rotor 112 and windings 330 to internal fins 1218 (and casing1216). The heat is then conducted from fins 1218 to external fins 1220.Airflow over exterior fins 1220 (and casing 1216) is employed todissipate the heat.

As best seen in FIG. 12, heat exchanger 1210 preferably includes acylindrical exterior cover 1222 to facilitate airflow over external fins1220. Cover 1222 is disposed coaxially with separator (casing) 1216,radially outward of heat exchanger external fins 1220. Cover 1222suitably nests within with exterior fan housing 1213 and is suitablyfastened at its rear end, and provides an outlet 1224 for heat exchanger1210 at its forward end. Respective axial channels 1228 communicatingwith the interior of fan housing 1213 are thus defined between adjacentexternal fins 1220, casing 1216, and heat exchanger cover 1222.

Internal fan 1212, suitably attached to or integral with rotor 112,generates an internal airflow directed over stator coils 330 (preferablythrough end turns 332), rotor 112 and through interior channels 1226 ofheat exchanger 1210. More particularly, internal fan 1212 is configuredto propel air outwardly, creating a negative pressure in the interior ofrotor 112, and an air stream, generally indicated by arrows 1230, isforced through channels 1226, cooling rotor casing 316 (and thus magnets318), and transferring heat to internal heat transfer fins 1218 andcasing 1216. Air stream 1230 exits channels 1226, flows throughfront-side end turns 332A, into stator central aperture 406. The airflowexiting the rear side of stator aperture 406 is directed to flow throughrear-side end turns 332B. This is suitably implemented using a deflector1232. After flowing through end turns 332B, the air stream flows throughrotor apertures 323, and is recirculated by fan 1206. Heat in statorcoils 330 and magnets 318 is thus dissipated and transferred to heatexchanger interior fins 1218. Fins 1218 are in thermal contact withcasing 1216 and external fins 1220 such that heat is conducted from fins1218 to external fins 1220. Airflow over exterior fins 1220 (and casing1216) is employed to dissipate the heat.

Airflow, generally indicated as 1234, over exterior fins 1220 issuitably generated by external fan 1212. External air provided throughintake 1214, is propelled outwardly within the interior of housing 1213by rotation of fan 1212, and forced through channels 1228, ultimatelyexiting through outlet 1224. If desired, filters (not shown) can beprovided over outlet 1224, and fan housing air intake 1214.

In some instances, it may be desirable to employ pressurized externalair from a source located remotely from sealed alternator unit. Such anembodiment 1400 is shown in FIG. 14. Sealed alternator 1400 issubstantially similar to alternator 1200 except that instead of beingdriven by a dedicated external fan 1212, alternator 1400 employs a rearhousing 1402, the interior of which communicates with heat exchangerexterior channels 1228, cooperating with a plenum 1404 and a suitableremote pressurized air source, such as a remote fan 1406. External airflow 1234 is supplied by remote fan 1406, directed through a plenum1404, through the interior of housing 1402 and channels 1228, andultimately exiting through outlet 1224.

An alternative embodiment of the present invention particularly adaptedfor use in sandy, wet, or otherwise harsh conditions, employs a locallysealed alternator cooperating with a double walled snorkel to provide acooling air from remote, less harsh source. Referring to FIG. 15, alocally sealed alternator 1500 cooperates with a snorkel 1502.Alternator 1500 is suitably similar in most respects to alternator 100described in conjunction with FIGS. 1-4. However, the front endplate116A (analogous to front endplate 116) and front bearing 118A (analogousto front bearing 118) are sealed, the rear endplate 122A (analogous torear endplate 122) includes a separate outer set of air passageways1504, in addition to air passageways 902, and (like the embodiment ofFIG. 4) tie rods 130 are disposed exteriorly of outer casing 128. Inaddition, alternator 1500 includes an air dam 1506, to separaterespective airflows, as will be described. Air dam 1506 is suitablyformed of felt, or integrally formed with rear endplate 122A.

Snorkel 1502 suitably includes generally vertical, generally cylindricalinner and outer chimney portions (1512A, 1514A, respectively) andtransverse inner and outer connecting portions (1512B, 1514B,respectively), formed by interior and exterior walls 1512 and 1514,respectively. The number of vertical and transverse portions is kept tothe lowest number possible (i.e.; the least number of bends) for anygiven installation to maximize air velocity. Inner wall 1512 (andproximate mouth of inner connecting portion 1512B) is disposed betweenendplate inner and outer passageways 902 and 1504; the outer diameter ofinner wall 1512 is suitably less than or equal to the inner diameter ofpassageway 1504, and the inner diameter of inner wall 1512 is greaterthan or equal to the outer diameter of passageways 902. An intake airway1516 communicating with endplate outer passageways 1504 is definedbetween exterior wall 1512 and interior wall 1514. An output airway 1520communicating with endplate inner passageways 902 is defined withininterior wall 1512. Intake airway 1516 and output airway 1520 aresuitably capped by first and second air filters 1518 and 1522,respectively. Input filter 1518, in effect, scrubs air introduced intothe alternator. Output filter 1520 prevents dust from entering thealternator through the exhaust when the alternator is not running.Interior chimney portion 1512A suitably extends beyond the externalchimney portion 1514A defined by exterior wall 1514. The mouths ofintake airway 1516 and output airway 1520 (filters 1518 and 1522) areboth disposed above a predetermined height, corresponding to the maximumdepth of water to be traversed by the vehicle in which alternator 1500is mounted. A suitable deflector 1524 is suitably disposed on thebetween air passageways 902 to minimize introduction of exhaust air fromoutput airway 1520 into intake airway 1516.

Snorkel 1502 is fixed to rear endplate 122A of alternator 1500 throughthe use of an adapter plate 1503. In the embodiment of FIG. 15, snorkel1502 and endplate 122A are secured by tie rods 130. Alternatively, themouth of exterior connecting portion 1514B can be force fit over theperiphery of rear endplate 122A, and if desired, secured by metalbanding. In any case, suitable sealant, gaskets or o-rings (not shown)are preferably employed to establish an essentially waterproof seal.Electric fan 126 is suitably disposed on an adapter plate 1503 (suitablydisk-shaped with respective air passageways there through) within theinterior of interior connecting portion 1512B, with blades arranged tocreate a negative pressure within the interior of rotor 112.

Fan 126 circulates air along a coolant path to create a cooling airflow1526 through the rotor and stator; air is taken in through filter 1518and intake airway 1516, flows through transverse outer connectingportion 1514B, outer air passageways 1504 in rear endplate 122A, thespace between outer casing 128 and the exterior of rotor casing 316,passageways 323 in rotor endcap 314, over end turns 332A, throughaperture 406 of stator core 328, over end turns 332B, through inner airpassageways 902 in rear endplate 122A, through fan 126, and throughsnorkel inner connecting portion 1512B, output airway 1520 and filter1522. Alternator 1500 is thus locally sealed, and can be submerged inwater up to the depth defined by snorkel 1502.

Fan 126 can be a conventional electric fan. However, it is desirablethat coolant circulation by fan 126 be maximized. A permanent magnet fandesign develops very high horse power for little in terms of energyinput, and facilitates large diameter blades for increased air velocityand pressure while still manifesting relatively small axial dimensions.

Accordingly, a fan specifically optimized for the available space isdesirable. Referring now to FIG. 16A, a first embodiment 1600A of such afan comprises: a stator frame 1602; a stator core 1604 and windings1606; front and back fan bearings 1608 and 1610; and a fan 1612. Statorframe 1602 is suitably includes a generally cylindrical body 1615 andsuitably includes fan bearings 1608 and 1610 centrally disposed therein.Stator frame 1602 is suitably secured to rear endplate 122A,concentrically with shaft 110. Fan stator core 1604 is suitablygenerally cylindrical, and disposed about stator frame body 1615.

Fan 1612 suitably comprises a cast fan body of engineered plastic,aluminum or other suitable material 1614, a fan rotor 1616, and aretaining fastener 1618. Fan body 1614 suitably includes a central hub1623 with a perpendicular central interior shaft 1624 (rotatablymaintained by bearings 1608 and 1610), connected to body 1614 byrespective crossarms forming respective passageways 1626. Passageways1626 communicate with snorkel inner connecting portion 1512B. Ifdesired, an air dam 1625, suitably formed of felt or low frictionmaterial, can be provided to between snorkel inner wall 1512 and fanrotor end cap 1612, to minimize movement of air between input and outputpassageways.

Fan rotor 1616 suitably fastened (i.e.: epoxied or other suitablefastening method) to fan body 1614, includes respective magnets 1632disposed on the interior thereof. Magnets 1632 are disposed in closeproximity to fan stator core 1604, separated only by a small air gap, toelectromechanically interact with fan stator windings 1606; electricalsignals applied to windings 1606 cause relative motion of magnets 1632,and hence fan 1612. Electrical power can be provided internally from thepower generated by alternator 1500, or can be supplied from the externalsource (e.g. a vehicle battery). Fan blades 1634 are disposed to moveair from snorkel exterior connecting portion 1514B through rear endplateouter passageways 1504. By disposing blades at the furthest diameterpossible, maximum air movement and pressure are provided. Fan bladespush air stream the 1526 through outer air passageways 1504 in rearendplate 122A. Air stream 1526 then circulates through the interior ofalternator 1500 as described in connection with FIG. 15, then exitsthrough inner air passageways 902 in rear endplate 122A, throughpassageway 1626 of fan 1600 and exhausts through snorkel innerconnecting portion 1512B which has been suitable fixed to adapter plate1503A, output airway 1520 and filter 1522 as described in connectionwith FIG. 15.

If desired, the fan blade can be configured to have respectivedifferently angled sections aligned with endplate inner and outerpassageways 902 and 1504 to push air into passageways 1504 and pull airout of passageways 902. Referring to FIG. 17, a fan 1700 employing sucha blade is suitably generally similar to fan 1600. However, fan 1700utilizes more compact stator frame 1702 (suitably without air passages),and a fan rotor 1704 including concentric inner and outer cylinders 1706(analogous to cylindrical body 1630) and 1708, respectively. A first setof fan blades 1710 (generally analogous to blades 1634) are provided onthe exterior of outer cylinder 1708 (connecting it to an outer cylinder1709). A second set of fan blades 1712 connect cylinders 1706 and 1708.

Outer cylinder 1708 is suitably concentric with and has approximatelythe same diameter inner snorkel wall 1512. Fan blades 1710 (like blades1634 in the embodiment of FIG. 16) are disposed to move air from snorkelexterior connecting portion 1514B through rear endplate outerpassageways 1504. Cylinders 1706 and 1708 are disposed such thatendplate inner passageway 902 is bracketed by the cylinders (e.g., theouter diameter of cylinder 1706 is less than or equal to the innerdiameter of passageway 902, and the outer diameter of passageway 902 isless than or equal to the inner diameter of outer cylinder 1708). Fanblades 1712 manifest a reversed angle as compared to fan blades 1710,such that a negative pressure is created at passageway 902 (i.e. air ispulled out of alternator 1500 through passageway 902). The side faces offan rotor 1614A proximate to endplate 122A are suitably maintained toclose tolerances, and separated from endplate 122A only by a relativelysmall air gap, generally indicated as 1714, suitably in the range of0.01 inch to 0.05 inch, and preferably 0.03 inch. Gap 1714 is smallenough that any migration of air between paths is insignificant. As thefan rotates it develops pressure in opposite directions the outer ringin and the inner ring out of the alternator creating the required flowto cool the alternator.

In sandy, dusty, wet, or otherwise harsh conditions (e.g. desert oragricultural applications) it may be desirable to filter air introducedinto the alternator. Dust and air born contaminates are potentiallyabrasive and sand very commonly carries iron compounds which canaccumulate on the permanent magnets (in the alternator and/or fan). Aninput filter is employed to, in effect, scrub air introduced into thealternator. An output filter is employed to prevent dust from enteringthe alternator through the exhaust when it is not running. Any suitablefiltering strategy may be employed, preferably with provisions forminimizing introduction of exhaust air into the alternator intake. Forexample, in the embodiment of FIG. 18A, fan 1600B, (with blades arrangedto create a negative pressure within alternator 1500) is disposed withina housing 1800 comprising a central cylindrical duct and a concentricdish shape deflector 1808. Fan 126 is suitably mounted concentricallywithin duct 1802 on a frame 126A (suitably with an outer peripheryconforming to the interior of duct 1802 with passages there through).Frame 126A may be integral with housing 1800. Duct 1802, suitablydisposed proximate to the side-wall of endplate 122A at one end, andclosed at the other, is suitably concentric with and disposed betweenendplate inner and outer passageways 902 and 1504; the outer diameter ofduct 1802 is suitably less than or equal to the inner diameter ofpassageway 1504, and the inner diameter of duct 1802 is greater than orequal to the outer diameter of passageways 902. Duct 1802 definesrespective input and output airways 1810 and 1804. Output airway 1804,within the interior of duct 1802, communicates with inner passageways902 in the alternator endplate 122A and exhausts radially through amouth 1805. A ring-type air filter 1806, concentric with duct 1802, isdisposed at the mouth of output airway 1804. Deflector 1808 is disposedabout the exterior of duct 1802, and provides a forward facing mouth1812. A ring-type air filter 1814, concentric with duct 1802, isdisposed within input airway 1810. Deflector 1808 cooperates with duct1802 to defining input airway 1810. Deflector 1808 with forward facingmouth 1812 tends to minimize introduction of exhaust air into alternator1500.

Introduction of exhaust air into alternator 1500 through the air intakecan also be minimized by relative disposition of the air intake andexhaust. For example, in FIGS. 18B, and 18C, the input airway opensradially exteriorly of duct 1802, and the output airway opens axially atthe rear. In the embodiment of FIG. 18B, input and output filter 1814and 1806 are both ring-type filters. Duct 1802 includes a stepped(increased diameter) portion 1802B, the sidewall of which cooperateswith endplate 122A to define the input airway. In the embodiment of FIG.18C, input filter 1814 is a ring-type filter and output filter 1806 is aflat plate type filter. In this case, the input airway is defined by anannular plate 1820 disposed on the exterior of duct 1802, in cooperationwith endplate 122A. If desired, duct 1802 and plate 1820 can be integralpart of fan frame 126A.

It is sometimes desirable to intake air from a location remote from thealternator, e.g. where the ambient air temperature in the vicinity ofthe alternator is higher than desirable. In the embodiment of FIG. 15,this is accomplished utilizing a snorkel attaching to the rear, andinitially extending axially from the alternator. In some applications,the axial extent of free space is limited, and it is desirable toprovide an air intake duct extending transversely relative to the axisof the alternator. Referring to FIG. 19, such a transversely ductedalternator is suitably generally similar to the embodiment of FIG. 1 8C,except that a conduit 1902 with a tangentially extending extension 1904,suitably capped with an air filter 1906, is employed rather than plate1820 and ring-type filter 1812.

Filters can also be utilized with the optimized fans of FIGS. 16 and 17.For example, referring to FIG. 20A, fan 1600 may be concentricallydisposed within a generally cylindrical fan housing 2000. Housing 2000suitably includes a concentric inner cylindrical wall 2002 that extendsinwardly and terminates proximate fan rotor end cap 1614, separated fromend cap 1614 only by a small gap 2004. The diameter of wall 2002 issuitably intermediate those of rotor body 1630, and air passageway 1626,preferably with an outer diameter equal to that of body 1630. Wall 2002defines respective input and output airways 2006 and 2008. Gap 2004 issmall enough that any migration of air between airways 2006 and 2008 isinsignificant. Input airway 2006, on the exterior of wall 2002,communicates with fan blade 1634, and ultimately with endplate outerpassageway 1504 and includes an intake adapted to receive a ring-typeair filter 2010, concentric with wall 2002. Output airway 2008, withinthe interior of wall 2002, communicates with passageways 1626, 1620 and1622 of fan 1600 and ultimately inner passageways 902 in the alternatorendplate 122A. Output airway 2006 exhausts through a filter 2009,suitably a flat plate type filter. The ability to reverse fan air flow2010 allows for an extension of airway 2008 using rubber flex tubing2012 or other suitable material to a more environmentally friendlylocation, feeding alternator 1500 with cooler air than would beavailable close to the alternator under very harsh conditions.Similarly, referring to FIG. 20B, fan 1700 may also be concentricallydisposed within fan housing 2000. In such case inner cylindrical wall2002 aligns with fans rotor outer cylinder 1708; the outer diameter ofwall 2002 is suitably equal to that of cylinder 1709.

As previously noted, the electrical current induced in the alternatorstator windings is typically applied to a bridge rectifier, sometimesregulated, and provided as an output. In some instances, the regulatedoutput signal is applied to an inverter to provide an AC output. Inaddition, electronic control systems to accommodate changes in the rotorspeed or changes in load characteristics may be employed. The componentsemployed in such electronic systems tend to be susceptible to heatdamage. Accordingly, it is desirable to dispose the electroniccomponents (particularly those components that produce heat duringoperation) into a die cast heat sink in the path of the coolest air,e.g., in the vicinity of the air intake. For example, referring to FIGS.21A and 21B, the heat producing electronic components 2100 are mountedon (pressed into) a heat sink 2102, which is, in turn, mounted withinair passageway 1504 in alternator endplate 121A. Heat sink 2102 isformed (e.g. machined or extruded) of a light thermally conductivematerial, e.g. aluminum, and includes a main rib 2104, with transverse(e.g. perpendicular) cooling fins 2106 and respective fastening tabs2108 at either end. Components 2100 are suitably mounted on main rib2104. Heat sink 2102 is contoured to fit within endplate passageway1504, such that the cooling air flow (generally indicated as 1526) runsover and between fins 2106. Heat sink 2102 is suitably fastened toendplate 121A by respective screws 2110 passing through tabs 2108 andthreading into endplate 121 A.

Alternatively, a heat sink bearing the electronic components can bedisposed within the input airway of a fan housing (e.g., 1800, 2000),snorkel (e.g., 1502), plenum (e.g., 1402) or the like cooperating withthe alternator. For example, components 2200 can be mounted on a heatsink 2202, which is in turn mounted in input airway 2006 of fan housing2000. Heat sink 2202 is suitably comb-like, formed (e.g. machined orextruded) of a light thermally conductive material, e.g. aluminum, witha base 2204, and transverse (e.g. perpendicular) cooling fins 2206.Components 2200 are suitably mounted on base 2204. The cooling air flow,generally indicated as 1526, flows through filter 2010, through therespective cooling fins 2206, and into the alternator through rearendplate passageway 1504.

In a sealed unit, such as the embodiments described in connection withFIGS. 12-14, the heat generating power components are preferablydisposed exteriorly of the sealed alternator, e.g., on a heat sinkdisposed on heat exchanger cover 222 within exterior channels 1228.

Referring to FIGS. 23A and 23B the heat producing electrical componentscan be mounted to a heat plate that uses the alternator coolant fluidsoutlined in FIGS. 9B and 9C. prior to entering the alternator cooledfluid flow through heat plate 2302. The heat producing components 2303are suitably fastened to heat plate 2302. Note that in FIG. 23B the sealof the alternator is maintained by locating the 2302 and 2303 exteriorof the alternator.

Although the present invention has been described in conjunction withvarious exemplary embodiments, the invention is not limited to thespecific forms shown, and it is contemplated that other embodiments ofthe present invention may be created without departing from the spiritof the invention. Variations in components, materials, values, structureand other aspects of the design and arrangement may be made inaccordance with the present invention as expressed in the followingclaims.

1. Power conversion apparatus comprising: a rotor comprising acylindrical casing, and a predetermined number of permanent magnetsdisposed in the interior of the casing, the rotor being adapted forrotation about the axis of the casing, a stator comprising a core and atleast one conductive winding, the core including a generally cylindricalouter peripheral surface and a predetermined number of slots formedtherein; the winding being wound around the core through the slots; thestator being concentrically disposed within the interior of the rotorcasing, with the stator core peripheral surface disposed proximate tothe rotor magnets, separated from the magnets by a predetermined gapdistance, such that relative motion of the rotor and stator causesmagnetic flux from the magnets to interact with and induce current inthe stator winding; and a cooling system for directing coolant flow intothermal contact with at least one of the winding and magnets, includingat least one passageway through the stator core.
 2. The apparatus ofclaim 1 wherein the stator winding includes end turns extendingoutwardly from the core, providing space between the end turns and core.3. The apparatus of claim 1 further including an end plate, wherein: thestator is mounted on the endplate; and the rotor is mounted for rotationrelative to the endplate.
 4. The apparatus of claim 3 wherein thecooling system further comprises at least a first passageway through theend plate in fluid communication with the stator core passageway.
 5. Theapparatus of claim 1 wherein the cooling system further comprises atleast a first passageway through the rotor in fluid communication withthe stator core passageway.
 6. The apparatus of claim 2 wherein thecooling system further comprises at least a first passageway through therotor in fluid communication with the stator core passageway.
 7. Theapparatus of claim 5 wherein the cooling system further comprises a fanmounted for rotation with the rotor disposed to move coolant through thestator core passageway.
 8. The apparatus of claim 6 wherein the coolingsystem further comprises a fan mounted for rotation with the rotordisposed to move coolant through the stator core passageway.
 9. Theapparatus of claim 4 wherein the coolant is air and the cooling systemfurther includes a forced air supply disposed to move air through theendplate passageway, and the stator core passageway.
 10. The apparatusof claim 1 further including at least one bumper disposed to prevent theposition of rotor from moving, in response to external forces, closerthan a predetermined distance to the stator, such that clashing betweenthe magnets and the stator is avoided.
 11. The apparatus of claim 3further including a shaft rotatably coupled to the endplate and therotor is coupled to the shaft for rotation therewith the shaft
 12. Theapparatus of claim 11 wherein: the shaft includes a tapered portiondisposed between the ends of the shaft at a predetermined positionrelative to the stator, the diameter of the tapered portion having apredetermined taper; the rotor includes a central through-bore having apredetermined taper corresponding to that of the tapered portion of theshaft; and the shaft is journaled through the rotor tapered bore, suchthat shaft tapered portion is received in the rotor bore, cooperation ofthe tapered rotor bore and tapered shaft portion positioning the rotorwith respect to the shaft and the stator.
 13. The apparatus of claim 9wherein the forced air supply comprises a fan asynchronous with respectto rotation of the rotor.
 14. The apparatus of claim 1 wherein thecooling system comprises a conduit extending through the stator corepassageway and into thermal contact with the winding.
 15. The apparatusof claim 1 wherein the disposition of at least one of the stator slotsand rotor magnets is skewed by a predetermined amount relative to theaxis of the stator.
 16. The apparatus of claim 2 wherein the coolingsystem comprises a conduit extending through the stator core passagewayand into thermal contact with the winding end turns.
 17. The apparatusof claim 16 further including a thermally conductive, electricallyinsulating element coupling the conduit and the winding end turns. 18.The apparatus of claim 16 wherein the conduit is encapsulated, togetherwith the winding end turns by a thermally conductive, electricallyinsulating material.
 19. The apparatus of claim 1 wherein the windingend turns are disposed in the path of coolant flow through the statorcore passageway.
 20. The apparatus of claim 14 further including coolingfins are thermally connected to the conduit.
 21. The apparatus of claim14 wherein coolant is liquid.
 22. The apparatus of claim 1 wherein thestator winding includes end turns bent into the path of coolant flowthrough the stator core passageway.
 23. The apparatus of claim 1 whereinthe coolant is air, and further including a forced air supply disposedto move air through the stator core passageway.
 24. The apparatus ofclaim 1 further including a shaft, first and second endplates, and anouter casing, wherein: the rotor casing, stator core, and outer casingare concentric with the shaft; the shaft is rotatably coupled to thefirst and second endplates; the stator is mounted on the second endplate; and the rotor is coupled to the shaft for rotation therewithbetween the first and second endplates and within the outer casing. 25.The apparatus of claim 11 wherein: the shaft includes a tapered portiondisposed between the ends of the shaft at a predetermined positionrelative to the stator, the diameter of the tapered portion having apredetermined taper; the rotor includes a central through-bore having apredetermined taper corresponding to that of the tapered portion of theshaft; and the shaft is journaled through the rotor tapered bore, suchthat shaft tapered portion is received in the rotor bore, cooperation ofthe tapered rotor bore and tapered shaft portion positioning the rotorwith respect to the shaft and the stator.
 26. The apparatus of claim 11wherein: the rotor comprises an endcap, a cylindrical casing, and apredetermined number of permanent magnets disposed in the interior ofthe casing; the casing and endcap being formed as an integral unit. 27.The apparatus of claim 26 wherein the the rotor and shaft are formed asan integral unit.
 28. The apparatus of claim 24 wherein: the rotorcomprises an endcap, a cylindrical casing having first and second ends,and a predetermined number of permanent magnets disposed in the interiorof the casing proximate to the second end, the rotor endcap isconcentrically mounted on the shaft for rotation with the shaft andconnected to the first end of the casing to dispose the casing coaxiallywith the shaft, the juncture of the endcap and shaft being at apredetermined axial position on the shaft; and the rotor endcap iscontoured such that the axial distance between the magnets and thejuncture of endcap and shaft is less than the axial distance between themagnets and the rotor casing first end and the axial length of thecasing interior in the vicinity of the stator core slots where thewindings are received is greater than the axial length of the casinginterior in proximity to the shaft.
 29. The apparatus of claim 24wherein coolant system further comprises a passageway a passagewaythrough the rotor in fluid communication with the stator corepassageway.
 30. The apparatus of claim 25 wherein the passageways aredisposed such that coolant flow is directed through the stator corepassageway, into thermal contact with at least a portion of the winding,through the rotor passageway, and into thermal contact with the magnets.31. The apparatus of claim 24 further including respective tie rodscooperating with the first and second end plates, compressing the firstand second end plates against the outer casing.
 32. The apparatus ofclaim 24 wherein the second endplate includes at least a firstpassageway therethrough in fluid communication with the stator corepassageway to permit coolant flow.
 33. The apparatus of claim 32 whereinthe coolant is air and the cooling system further includes a forced airsupply disposed to move air through the endplate passageway, and thestator core passageways.
 34. The apparatus of claim 33 wherein theforced air supply is asynchronous relative to the shaft.
 35. Theapparatus of claim 33 wherein the forced air supply comprises anelectric fan.
 36. The apparatus of claim 35 wherein the electric fan ismounted on the second endplate.
 37. The apparatus of claim 33 whereinthe forced air supply comprises a conduit communicating with the secondend plate to provide air from a location remote from the secondendplate.
 38. The apparatus of claim 33 wherein the first endplate issealed, the second endplate has at least two separate air passageways,and further including a conduit comprising a double wall snorkel havinga first airway communicating with one of the endplate passageways and asecond airway communicating with the other endplate passageway, and theforced air supply is disposed to cause intake of air through one snorkelairway, air movement through one of the endplate passageways, the rotorand stator core, and the other endplate passageway and to exhaustthrough the other snorkel airway.
 39. The apparatus of claim 38 whereinthe forced air supply includes a fan having respective oppositelypitched, concentrically disposed blades, one blade positioned to driveair into the endplate passageway communicating with the intake snorkelairway, and the other blade positioned to exhaust air from the otherendplate passageway.
 40. The apparatus of claim 33 wherein the forcedair supply comprises a fan disposed to rotate with the shaft.
 41. Theapparatus of claim 32 wherein the first endplate includes a passagewayin fluid communication with the rotor passageway a first coolant flowpath is provided between the second endplate passageway and firstendplate passageway through the stator core passageway and rotorpassageway a second coolant flow path is provided between the secondendplate passageway and second endplate passageway through the spacebetween the rotor casing and the outer casing.
 42. The apparatus ofclaim 32 wherein: the second endplate includes a second passageway; acoolant flow path is provided between the second endplate first andsecond passageways through the stator core passageway, the rotorpassageway, and the space between the rotor casing and the outer casing.43. The apparatus of claim 24 wherein said first and second endplatesare sealed and said casing comprises a heat exchanger.
 44. The apparatusof claim 43 including an internal fan disposed for rotation with saidshaft, for circulating coolant through the rotor and stator core andinto contact with the heat exchanger.
 45. The apparatus of claim 1wherein the cooling system further comprises at least one of: looselywrapped winding end turns extending outwardly from the core disposed inthe path of airflow through the stator core passageway; passagewaysthrough the rotor for directing a portion of the airflow through thestator core passageway over elements in thermal contact with themagnets; an airflow source that is asynchronous with respect to rotorrotation; deflectors for directing a portion of the airflow through thestator core passageway into thermal contact with at least one of thewinding end turns and magnets; a conduit extending through the statorcore passageway and into thermal contact with the winding end turns; anda conduit communicating with the stator core passageway for providingair from a remote source.
 46. Power conversion apparatus comprising:first and second endplates; a shaft rotatably coupled to the first andsecond endplates; a cylindrical outer casing disposed concentric withthe shaft between, and coupled to, the first and second endplates; arotor comprising a cylindrical casing disposed concentric with the shaftbetween the first and second endplates and within the outer casing, andcoupled to the shaft for rotation therewith, the rotor including apredetermined number of permanent magnets disposed on the interior ofthe casing; a stator comprising a core and at least one conductivewinding, the core having a generally cylindrical outer peripheralsurface with a predetermined number of slots formed therein, with thewinding wound around the core through the slots; the stator core beingfixed to the second endplate, with peripheral surface disposedconcentric with, and within the interior of, the rotor casing proximateto the rotor magnets, separated from the magnets by a predetermined gapdistance, such that relative motion of the rotor and stator causeselectromagnetic interaction between the magnets and the stator winding.47. The apparatus of claim 46 further including a cooling system fordirecting coolant flow over the winding, including at least onepassageway through the rotor and at least one passageway through thestator core.
 48. The apparatus of claim 46 further including at leastone bumper disposed to prevent the position of rotor from moving, inresponse to external forces, closer than a predetermined distance to thestator, such that clashing between the magnets and the stator isavoided.
 49. The apparatus of claim 46 wherein the first and secondendplates each include a central aperture having a bearing disposedtherein for concentrically receiving the shaft, and a feature concentricwith the central aperture for locating and mounting the outer casing,and the second endplate includes a central hub concentric with theaperture projecting axially in the direction of the first endplate, thestator core being fixed to the second endplate hub.
 50. Power conversionapparatus comprising a shaft, a stator; and a rotor, the shaft, statorand rotor being coaxially disposed, with the rotor mounted on the shaft,the stator including at least one winding, and the rotor including aplurality of permanent magnets disposed proximate to the stator,separated from the stator by a predetermined gap distance, such thatrelative motion of the rotor and stator causes magnetic flux from themagnets to interact with and induce current in the stator winding,wherein: the shaft includes a tapered portion disposed between the endsof the shaft at a predetermined position relative to the stator, thediameter of the tapered portion having a predetermined taper; the rotorincludes a central through-bore having a predetermined tapercorresponding to that of the tapered portion of the shaft; and the shaftis journaled through the rotor tapered bore, such that shaft taperedportion is received in the rotor bore, cooperation of the tapered rotorbore and tapered shaft portion positioning the rotor with respect to theshaft and the stator.
 51. The apparatus of claim 50 wherein thepredetermined taper is in the range of 1 in. diameter per 7 inches oflength to 1 in. diameter per 16 inches of length
 52. The apparatus ofclaim 50 wherein the predetermined taper is on the order of 1 in. perfoot.
 53. The apparatus of claim 50 further including first and secondendplates, an outer casing and a plurality of tie rods, cooperating tomaintain alignment of the shaft, rotor, and stator, wherein: The shaftis rotatably held by the endplates, in axial alignment with theendplates; The stator is affixed to one of the endplates, and maintainedin predetermined disposition with respect thereto; and The outer casingis disposed between the front and rear endplates with tie rods disposedto compress the front and rear endplates against outer casing.
 54. Theapparatus of claim 50 wherein: The rotor comprises an endcap, and acylindrical casing, the magnets being disposed on the interior of thecasing; the stator is disposed within the rotor casing.
 55. Theapparatus of claim 50 wherein the stator comprises a core includingfront and back side-faces and a generally cylindrical outer peripheralsurface with a predetermined number of slots formed therein; and thestator winding is wound around the core, such that with respect to atleast one end face, the winding passes through a first slot, forms anend turn extending outwardly beyond the core side face, providing aspace between the end turn and end face, then passes back throughanother slot.
 56. The apparatus of claim 50 further including a fan andrespective air passageways disposed to circulate air moved by the fanover the winding end turns.
 57. The apparatus of claim 50 wherein thefan is electrically driven.
 58. The apparatus of claim 50 furtherincluding a front endplate, a rear endplate, an outer casing,cooperating to maintain alignment of the shaft, rotor, and stator,wherein the air passageways comprise at least one air passageway throughthe rear end plate, at least one air passageway through the stator core,at least one air passageway through the rotor endcap and at least oneair passageway through the front end plate.
 59. The apparatus of claim50 wherein the rotor endcap comprises a peripheral portion connecting tothe casing, a central hub having the tapered bore and a connectingportion connecting the peripheral portion to the central hub andincluding at least one air passageway therethrough.
 60. The apparatus ofclaim 50 wherein the connecting portion comprises a plurality ofcrossarms.
 61. The apparatus of claim 50 wherein the crossarms aredisposed at a non-perpendicular angle relative to the axis of the rotorcasing such that the axial length of the casing interior is greater inproximity to the casing than in proximity to the shaft.
 62. Theapparatus of claim 50 wherein the rotor endcap is contoured such thatwhen the shaft tapered portion is received in the rotor bore, the shafttapered portion is within the interior of the rotor casing.
 63. Theapparatus of claim 50 wherein at least a portion of rotor endcap isdisposed an angle other than 90° relative to the rotor casing, wherebythe axial distance between the point of connection of the rotor to theshaft and the magnets is less than the axial length of the rotor casing.64. The apparatus of claim 50 wherein the rotor endcap connectingportion is contoured such that the rotor hub is disposed within theinterior of the rotor casing.
 65. Power conversion apparatus comprising:a first and second endplates; a rotatable shaft disposed concentricallywith and perpendicular to the end plates; a rotor comprising an endcap,a cylindrical casing having first and second ends, and a predeterminednumber of permanent magnets disposed in the interior of the casingproximate to the second end, the rotor endcap being concentricallymounted on the shaft for rotation with the shaft and connected to thefirst end of the casing to dispose the casing coaxially with the shaft,the juncture of the endcap and shaft being at a predetermined axialposition on the shaft; a stator comprising a core and at least oneconductive winding, the core including first and second side-faces and agenerally cylindrical outer peripheral surface with a predeterminednumber of slots formed therein; the winding being wound around the corethrough the slots; the stator being mounted on one of the end plates,positioned concentrically with the shaft and rotor casing within theinterior of the rotor casing, with the stator core peripheral surfacedisposed proximate to the rotor magnets, separated from the magnets by apredetermined gap distance, such that relative motion of the rotor andstator causes magnetic flux from the magnets to interact with and inducecurrent in the stator winding; and an outer casing, concentric with theshaft, coupled to the first and second end plates; the rotor endcapbeing contoured such that the axial distance between the magnets and thejuncture of endcap and shaft is less than the axial distance between themagnets and the rotor casing first end and the axial length of thecasing interior in the vicinity of the stator core slots where thewindings are received is greater than the axial length of the casinginterior in proximity to the shaft.
 66. Power conversion apparatuscomprising a shaft, a stator; and a rotor, the shaft, stator and rotorbeing coaxially disposed, with the rotor mounted on the shaft, thestator including at least one winding, and the rotor including aplurality of permanent magnets disposed proximate to the stator,separated from the stator by a predetermined gap distance, such thatrelative motion of the rotor and stator causes magnetic flux from themagnets to interact with and induce current in the stator winding,wherein: the stator comprises a core including front and back side-facesand a generally cylindrical outer peripheral surface with apredetermined number of slots formed therein, the stator winding iswound around the core, such that with respect to at least one end face,the winding passes through a first slot, forms an end turn extendingoutwardly beyond the core side face, providing a space between the endturn and end face, then passing back through another slot, wherebydissipation of heat generated in the winding is facilitated.
 67. Powerconversion apparatus comprising a shaft, a stator including at least onewinding; and a rotor including a plurality of permanent magnets, theshaft, stator and rotor being coaxially disposed, with the rotor mountedon the shaft, such that, in the absence of external forces, the rotor isdisposed in a predetermined position relative to the stator with themagnets proximate to the stator, separated from the stator by apredetermined gap distance, such that relative motion of the rotor andstator causes magnetic flux from the magnets to interact with and inducecurrent in the stator winding, further including at least one bumperdisposed to prevent the position of rotor from deviating, in response toexternal forces, more than a predetermined amount from the predeterminedposition relative to the stator, such that clashing between the magnetsand the stator is avoided